RE:Dfly!At N 07 27' 47.99" - W 056 24' 42.00" Akh..me Heading to Mall see what I can get at low low price..lol Rain soaked me hammock this morning ..cementing at 20000 feet not my area of expertise sounds danegurrss ...Low-pressure wells that absorb easily The typical low-pressure lost-circulation zone includes low-pressure fractured reservoirs and sandstone reservoirs. A drilling fluid column pressure higher than reservoir pressure may cause leakage of a large quantity of drilling fluid during drilling. Cement slurry column pressure higher than reservoir pressure may also cause a leakage of cement slurry during cementing. Lost circulation during cementing may make the reservoir uncemented or imperfectly cemented or cause an insufficient cement slurry return height, which may cause interzone communication, thus causing sloughing because the water in water-bearing formation invades the restraining barrier. In addition, the leakage of cement slurry may plug fractures and cause formation damage. 2. High-pressure leaking wells that easily absorb A high-pressure well that easily absorbs often presents blowout and leaking because there simultaneously are a low-pressure lost-circulation zone and a high-pressure gas reservoir in the same open hole section. In general, there are two situations. One is that a lost-circulation zone is above a high-pressure gas reservoir. During drilling by using low-density drilling fluid or continuous drilling after sealing, a high-pressure gas reservoir is drilled-in. Increasing drilling fluid density may cause an overflow due to the lost-circulation zone, thus inducing blowout. The other situation is that a lost-circulation zone is below a high-pressure gas reservoir. During drilling the upper part the gas reservoir has been suppressed; however, when the lower lost-circulation zone is drilled in, lost circulation is generated. Thus the whole fluid column pressure in the borehole may be decreased, and an overflow may be caused, or even a blowout may be caused. In many deep wells, cement slurry is required to be returned to the surface, thus aggravating the risk of lost circulation during cementing. Daylighting Helmut F.O. Meller, in Sustainability, Energy and Architecture, 2013 9.8 Visual Performance Visual function depends on the specific task and the parameters of luminance, contrast and color rendering. Orientation, e.g., while walking through a circulation zone, requires lower visual performance than accurate work on objects which have small scale detail for long periods of time. The variation in individual visual capability, e.g., its decrease with age, also needs to be taken into consideration. Basically, visual performance improves with illuminance, and how well the task in hand is lit. Illuminances of 1,000 to 6,000 lux are recommended for high visual performance (Lange, 2002). This only applies to situations where the contrast is good, and produces a predominant direction of light and a resulting shadow. If the light is diffuse and without shadows, our three dimensional perception of objects is very poor. Compared to these recommended values, minimum task illuminances for lighting in national and international directives, e.g., DIN EN 12464 [13], are much lower (100 to 1000 lux, depending on the type of task). They define the lowest acceptable standard, and take into account technical and financial inputs into artificial lighting. These values should not be taken as optimal or recommended levels. Daylighting design and technology can realize much higher illuminances to promote optimal visual performance and comfort for many hours of the day, in economical and sustainable ways. Artificial light has to be used at night, and during the day when daylight levels fall below the minimum requirements. Such lighting should of course supply better than standard minimum illuminances for reasons of improved comfort, health and visual function. Special Cements Martin Liska, ... John Bensted, in Lea's Chemistry of Cement and Concrete (Fifth Edition), 2019 Thixotropic Agents Thixotropic agents are added to oil-well cement slurries to produce thixotropic properties downhole, which are needed to overcome problems of lost circulation by sealing off lost circulation zones or achieving good annular fill across incompetent zones. Examples of thixotropic agents include calcium sulfate hemihydrate (CaSO40.5H2O), which functions on the basis of its false setting properties4749 in hydrating to gypsum: (13.2) and which can be used (ca. 8%12% by weight of cement) up to ~ 80C, and mixtures of aluminium sulfate and iron(II) sulfate50 that generate gypsum in situ and proceed to the formation of ettringite in the cement slurry. Proprietary organic-based mixtures, such as guar gumbenzoquinonesodium carbonate mixture51 and titanium, zirconium or hafnium chelates with cross-linkable agents, such as titanium chelates with water-soluble cellulose ethers, poly(vinyl alcohol) and acrylamide polymers,52 are also sometimes used. Completion and Perforating Fluids Wan Renpu, in Advanced Well Completion Engineering (Third Edition), 2011 Aero-Fluid Aero-fluid means the circulation fluid composed of air or natural gas, corrosion inhibitor, and drying agent. Aero-fluid is often used for drilling of lost-circulation zones, strongly sensitive reservoirs, vuggy low-pressure zones, and low-pressure payzones, due to low aero-fluid density. The penetration rate can be increased by three to four times in comparison with the conventional drilling fluid. The aero-fluid has the features of high penetration rate, short drilling time, and low drilling cost. Special equipment, such as air compressors, is needed on the well site when an aero-fluid is used for drilling. In general, aero-fluid drilling can be effectively conducted under a surface injection pressure of 0.71.4 MPa and an annular velocity of 762914 m/min. The usage of aero-fluid is often limited by well depth, formation water production, and an unstable borehole wall. FLUID DYNAMICS IN WELL CONTROL Robert D. Grace, in Blowout and Well Control Handbook, 2003 Example 5.2 Given: Depth, D = 20,000 feet Bottomhole pressure, Pb = 20,000 psi Casing shoe at, Dshoe = 10,000 feet Fracture gradient at shoe, Fg = 0.9 psi/ft The production is gas and the well is blowing out underground. Required: Approximate the surface pressure if the gas is permitted to migrate to the surface. Determine the surface pressure if 15-ppg mud is continuously bullheaded into the annulus. Solution: If the gas is permitted to migrate to the surface, the surface pressure will be approximately as follows: With 15-ppg mud bullheaded from the surface to the casing shoe at 10,000 feet, the surface pressure would be Therefore, as illustrated in Example 5.2, without the bullheading operation, the surface pressure would build to 8000 psi. At that pressure surface operations are very difficult at best. If 15-ppg mud is bullheaded into the lost circulation zone at the casing shoe, the surface pressure can be reduced to 200 psi. With 200 psi surface pressure, all operations such as snubbing or wire line are considerably easier and faster. A deep well in the southern United States got out of control while tripping. The conditions and wellbore schematic are presented in Figure 5.3. Sign in to download full-size image Figure 5.3. Wellbore Schematic. Since there were only 173 feet of open hole, it was concluded that the well would probably not bridge. However, when the cast iron bridge plug was set inside the drillpipe in preparation for stripping in the hole, the flow began to diminish. Within the hour, the flow declined to a small, lazy flare. The well had obviously bridged. The primary question at that point was the location of the bridge. Normally, bridging occurs in the bottom hole assembly. The velocity is low deep in the well adjacent to the bottom hole assembly. The changes in diameter provide opportunity for the accumulation of formation particulate. In this case, drillpipe protector rubbers had been used. It is not unusual for protector rubbers to be problematic in the presence of high temperature gas. Due to the presence of the rubbers, the bridge could be high in the well. A deep bridge would be acceptable since sufficient hydrostatic could be placed above the bridge to compensate for the high formation pressure. A shallow bridge would be very dangerous since full shut-in pressure could easily be immediately below the surface and held only by a few feet of packed debris. Since the well was continuing to produce a small quantity of gas, it was considered that a temperature survey could identify the bridge. It was anticipated that the expansion of the gas across the bridge would result in a significant temperature anomaly. Accordingly, a temperature survey was run and is presented as Figure 5.4. As illustrated in Figure 5.4, interpretation of the temperature indicated that the bridge was around the bottom hole assembly. Accordingly, the annulus was successfully loaded with 432 barrels (the calculated volume was 431 barrels) of 20 ppg mud. Sign in to download full-size image Figure 5.4. Temperature Analysis Well Bridged, August 13, 1998. In summary, bullheading operations can have unpleasant results and should be thoroughly evaluated prior to commencing the operation. Too often, crews react to well control problems without analyzing the problem and get into worse condition than when the operation began. Remember, the best well control procedure is one that has predictable results from the technical as well as the mechanical perspective. Drilling Fluid Components Ryen Caenn, ... George R. , in Composition and Properties of Drilling and Completion Fluids (Seventh Edition), 2017 Lost Circulation Additives Filtration control is an important property of a drilling fluid, particularly when drilling through permeable formations in which the hydrostatic pressure exceeds the formation pressure. It is important for a drilling fluid to quickly form a filter cake which effectively minimizes fluid loss, but which also is thin and erodable enough to allow product to flow into the wellbore during production (Jarrett and Clapper, 2010). A few fluid loss additives for drilling fluids are summarized next for quick reference. There are a number of methods that have been proposed to help to prevent the loss of a circulation fluid (Messenger, 1981). Some of these methods use fibrous, flaky, or granular materials to plug the pores as the particulate material settles out of the slurry. Lost circulation additives are summarized in Table 13.3. Other methods propose to use materials that interact in the fissures of the formation to form a plug of increased strength. Table 13.3. Lost Circulation Additives Material References Encapsulated lime Walker (1986) Encapsulated oil-absorbent polymers Delhommer and Walker (1987a), Walker (1987, 1989) Hydrolyzed poly(acrylonitrile) Yakovlev and Konovalov (1987) Divinylsulfone, cross-linked Poly(galactomannan) gum Kohn (1988) PU foam Glowka et al. (1989) Partially hydrolyzed poly(acrylamide) 30% hydrolyzed, cross-linked with Cr3+ Sydansk (1990) Oat hulls House et al. (1991) Rice products Burts (1992, 1997) Waste olive pulp Duhon (1998) Nut cork Fuh et al. (1993), Rose (1996) Pulp residue waste Gullett and Head (1993) Petroleum coke Whitfill et al. (1990) Shredded cellophane Burts (2001) Water Swellable Polymers Certain organic polymers absorb comparatively large quantities of water, e.g., alkali metal poly(acrylate) or cross-linked poly(acrylate)s (Green, 2001). Such water-absorbent polymers, insoluble in water and in hydrocarbons, can be injected into the well with the objective of encountering naturally occurring or added water at the entrance to and within an opening in the formation. The resulting swelling of the polymer forms a barrier to the continued passage of the circulation fluid through that opening into the formation. The hydrocarbon carrier fluid initially prevents water from contacting the water-absorbent polymer until such water contact is desired. Once the hydrocarbon slug containing the polymer is properly placed at the lost circulation zone, water is mixed with the hydrocarbon slug so that the polymer will expand with the absorbed water and substantially increase in size to close off the lost circulation zone (Bloys and Wilton, 1991; Delhommer and Walker, 1987; Walker, 1987, 1989). The situation is similar to an oil-based cement. The opposite mechanism is used by a hydrocarbon-swellable elastomer (Wood, 2001). Anionic Association Polymer Another type of lost circulation agent is the combination of an organic phosphate ester and an aluminum compound, e.g., aluminum isopropoxide. The action of this system as a fluid loss agent seems to be that the alkyl phosphate ester becomes cross-linked by the aluminum compound to form an anionic association polymer, which serves as the gelling agent (Reid and Grichuk, 1991). Other lost circulation additives can be encapsulated. The encapsulation is dissolved and the material swells to close fissures. Microbubbles in a drilling fluid can be generated by certain surfactants, and polymers known as aphrons are a different approach to reduce the fluid loss (Ivan et al., 2001). Permanent Grouting Lost circulation also can be suppressed by grouting permanently, either with cement (Allan and Kukacka, 1995; Cowan and Hale, 1994) or with organic polymers that cure in situ. Harmful phenomena in modernized boilers Marek Pronobis, in Environmentally Oriented Modernization of Power Boilers, 2020 8.5.3 Formation of medium temperature (MT) ash deposits Medium-temperature (MT) deposits can be found in flue gas temperatures between the softening temperature tA and the dew point temperature. Unlike the HT deposits, they form mainly on the trailing part of tubes in the form of unilateral wedge-shaped deposits (Fig. 8.31), which can transform into bilateral shape and further into the ash bridges connecting the tubes. The chemical composition of MT deposits practically does not differ from the composition of fly ash. Significantly higher is only the proportion of sulfates [106] (Fig. 8.37). The situation is different in the case of the grain composition of fly ash and the resulting fouling, wherein the proportion of the finest fractions is much higher. Analysis of adhesive and destructive forces acting on fly ash particles [1,106,109] also confirms that the main component of MT deposits should be particles with a diameter not exceeding 30 m. Because the flue gas in a solid fuel boiler generally contains significant amounts of coarser ash particles, and the increase in flue gas velocity in the spaces between the tubes causes high aerodynamic forces, very low mechanical strength MT deposits can occur only in certain specific zones of the tube bank. The spaces occupied by deposits correspond to the circulation zones in the turbulent boundary layer on the trailing surface of the tubes and the zone near the center of the inlet surface. The range and shape of the circulation zones in tube banks of staggered arrangement are presented in Ref. [116]. Exemplary deposit shapes for different flue gas velocities that are shown in Fig. 8.38 were taken from Ref. [108]. Sign in to download full-size image Figure 8.38. Range and shape of circulation zones and MT deposits in a staggered tube bank. In tube banks with the in-line arrangement, the circulation zone fills practically all the space between successive tubes in the flow direction. Therefore, deposits can easily turn into ash bridges. The mechanism of MT fouling formation was extensively analyzed in [106,117,109]. The distribution of the mass flow of particles reaching the tube surface depends on the local circulation intensity in the turbulent boundary layer. It can be assumed that the contact frequency of particles and tube is distributed similarly to well known (and mutually analogous) distributions of heat and mass transfer intensity on the tube. This assumption is all the more true, the smaller the ash particles transported by the flue gas are. Commonly is assumed that by dp < 20="" m="" the="" particles="" are="" moving="" without="" inertia="" according="" to="" eddies="" of="" turbulent="" flue="" gas="" flow.="" investigations="" confirmed="" that="" ash="" components="" of="" such="" a="" particle="" size="" are="" the="" initial="" layer="" of="" mt="" fouling.="" as="" the="" thickness="" of="" the="" deposit="" increases,="" the="" proportion="" of="" larger="" particles="" that="" are="" stuck="" in="" the="" soft="" deposit="" also="" increases.="" if="" the="" flue="" gas="" contains="" ash="" with="" the="" particle="" size="" larger="" than="" 30="" m="" then="" the="" barrier="" to="" the="" expansion="" of="" the="" deposit="" is="" the="" boundary="" of="" the="" circulation="" zone="" beyond="" which="" the="" large="" mass="" of="" coarse="" particles="" having="" strong="" erosive="" properties="" prevents="" the="" deposition="" of="" ash.="" therefore,="" the="" formation="" of="" ash="" bridges="" in="" coal="" boilers="" (except="" wet="" bottom="" ones)="" is="" possible="" only="" in="" in-line="" tube="" banks="" or="" in="" the="" staggered="" with="" spacings="" st="">> sL and sL D. Studies have shown that in boilers fired with coal, the deposit typically does not fill the whole circulation zone, which is due to the erosive action of particles moving through complex trajectories as a result of reflections from tubes. If the flue gas does not contain coarse ash particles (heavy-oil fired or wet-bottom boilers), the fouling can fill the whole circulation zone [118]. Described phenomena prefer a relatively more intensive adhesion of small particles of low density. The result is an increase in the proportion of sulfates in deposits. They are mainly formed by the sulfation of calcium and magnesium oxides produced by the prior calcination (thermal decomposition) of Ca and Mg carbonates contained in ash. During calcination, the crystalline carbonate structure changes to produce very fine porous (low-density) CaO and MgO particles. The processes described above are intensified by introducing additional alkaline compounds to the furnace. Their source may be the high-temperature (dry) desulfurization or co-firing biomass with coal. Especially significant is the introduction of Ca and Mg hydroxides and dolomite (CaMg(CO3)2), whose calcination results in very fine particulates (generally dp < 5 m), while the size of carbonate calcination grains is significantly larger, within 10-50 m [119]. the final size of particles also depends on calcination temperature - with increased temperature the grains are coarser. the above observations indicate the high influence of the phenomena occurring in the furnace not only on the processes of slagging and formation of ht fouling but also on the nature of mt deposits covering the tubes in the convection part of the boiler. with accuracy sufficient for technical purposes, this effect can be determined computationally by the formulae (8.56) and (8.57). once the increased amounts of calcium and magnesium compounds are added to the combustion chamber, the b/a value (8.54) increases. as a result, the effectiveness number of the heat exchanger changes according to the equation (assuming the mean exponent for in-line and staggered tube banks) (8.59) this proves that as the amount of basic substances increases, the value of f will decrease. an additional factor lowering f is the enrichment of fly ash with very fine particles, such as cao resulting from calcination of calcium hydroxide (decrease of r0.03). sometimes the presence of sulfates and other cementitious compounds in loose powdery deposit can cause the formation of fouling of considerable strength. strengthening occurs after reaction with water that may occur in the boiler either as a result of atmospheric moisture condensation on a standstill and in case of inadequate surface cleaning of tubes with water. this phenomenon can make impossible the cleaning of heating surfaces by means of sootblowing. similarly, the lt deposits are formed at temperatures lower than the dew point temperature. introduction bill rehm, ... abdullah al-yami, in underbalanced drilling: limits and extremes, 2012 1.13.2 mud displacement when pulling pipe underbalanced wells make hole fill up easy when tripping, but it is very different from a normal trip fill up. the following items are important when pulling out of the hole (poh): if there is no permeability, the bottom-hole pressure could be kept at about the same pressure by adding enough fluid to compensate for drillpipe displacement in the wet part of the hole. if there is reasonable fluid permeability and/or lost circulation zones, the fluid is going to seek its own level. nothing in the way of the drillpipe hole fill up will make a difference. this is a place where a mud cap might be used to keep the formation fluid from coming to the surface (see section 1.13.4 mud cap or chapter 7, mud cap drilling in fractured formations). if there is a danger of wellbore fluid or gas to the surface, fill up can be done on a normal drilling basis. the ideal solution would be a down-hole casing valve. the next best choice is the mud cap. it is a heavier, thicker column of mud placed at some distance downhole to overbalance the well and keep formation fluid from coming to the surface. advances in managed pressure drilling technologies m.rafiqul islam, m.enamul hossain, in drilling engineering, 2021 5.6.4 candidate screening candidate screening is a filtering process to match the particular udt to the problem faced by the well section. a detailed screening allows the engineer to identify the right technique and, most importantly, the correct spread of equipment. the comparison below highlights a generic screening result for these two techniques. 5.6.4.1 underbalanced drilling ubd is an excellent candidate for depleted formations, especially when production enhancement is the target. ubd is and has been applied in formations with the following characteristics: depleted formations for production enhancement; formation damage prevention; storage or injector wells; depleting nuisance zones, such as high-pressure, low-volume gas pockets in top-hole sections; real-time formation evaluation (single point production test or drawing productivity index while drilling); lost circulation zones; tombstone rock drilling in intermediate hole section. 5.6.4.2 managed pressure drilling due to its zero influx policy, mpd can be applied in sections that are prone to lost circulation, areas where stuck pipe is an issue, or in hpht reservoirs to avoid npt, mainly in the form of high mw or ecds. to date, 70% of mpd wells have needed ecd control to avoid reaching fracture gradient or creating drilling-induced fractures. therefore, most mpd today revolves around ecd or pseudo-mw control without increasing any solids in the mud to create the same effect of ecd as created by a weighted mud. a few cases have also seen a reduction in casing strings by controlling ecd at the sandface. once the desired td is reached, the casing is landed to secure the section without adding any additional strings. mpd has also seen a great value in hpht wells, where longer open holes are able to be drilled, which were not possible with the traditional way of increasing mw to control the formation pressure. in summary, ubd is primarily concerned with production enhancement from depleted reservoirs. mpd works with issues that are related to high mws and ecds that result in shorter wellbore length, challenging windows between pore and fracture gradient or areas where lost circulation is induced due to dilation of near-wellbore fractures. the bottom hole circulating pressure throughout an mpd operation remains slightly above the pore pressure. casing and pipeline corrosion george v. chilingar, ... ghazi d. al-qahtani, in the fundamentals of corrosion and scaling for petroleum & environmental engineers, 2008 5.2.6 liners liners are the pipes that do not reach the surface, and are suspended from the bottom of the casing string above. usually, they are set to seal off troublesome sections of the well or through the producing zones for economic reasons. basic liner assemblies are shown in figure 5.2. they include drilling liner, production liner, tieback liner, scab liner, and scab tieback liner (brown-hughes co., 1984). sign in to download full-size image figure 5.2. basic liner systems. (after brown-hughes co., 1984)copyright 1984 1. drilling liner: drilling liner is a section of casing that is suspended from the existing casing (surface or intermediate casing). in most cases, it extends downward into the openhole and overlaps the existing casing by 200 to 400 ft. it is used to isolate abnormal formation pressure, lost circulation zones, heaving shales and salt sections, and to permit drilling below these zones without having well problems. 2. production liner: production liner is run instead of full casing to provide isolation across the production or injection zones. in this case, intermediate casing or drilling liner becomes part of the completion string. 3. tieback liner: tieback liner is a section of casing extending upwards from the top of the existing liner to the surface. this pipe is connected to the top of liner (figure 5.2b) with a specially designed connector. production liner with tieback liner assembly is most advantageous when exploratory drilling below the productive interval is planned. it also gives rise to low hanging weights in the upper part of the well. 4. scab liner: scab liner is a section of casing used to repair existing damaged casing. it may be cemented or sealed with packers at the top and bottom (figure 5.2c). 5. scab tieback liner: scab tieback liner is a section of casing extending upward from the existing liner, but which does not reach the surface and is normally cemented in place. scab tieback liners are commonly used with cemented heavy wall casing to isolate salt sections in deeper portions of the well. possible leaks across the hanger and the difficulty in obtaining a good primary cement job due to the narrow annulus must be taken into consideration. recommended publications publication cover applied thermal engineering journal publication cover chemical engineering research and design journal publication cover international journal of thermal sciences journal publication cover building and environment journal elsevier logo about sciencedirect remote access shopping cart advertise contact and support terms and conditions privacy policy we use cookies to help provide and enhance our service and tailor content and ads. by continuing you agree to the use of cookies. copyright 2021 elsevier b.v. or its licensors or contributors. sciencedirect is a registered trademark of elsevier b.v. relx group home page 5="" m),="" while="" the="" size="" of="" carbonate="" calcination="" grains="" is="" significantly="" larger,="" within="" 10-50="" m="" [119].="" the="" final="" size="" of="" particles="" also="" depends="" on="" calcination="" temperature="" -="" with="" increased="" temperature="" the="" grains="" are="" coarser.="" the="" above="" observations="" indicate="" the="" high="" influence="" of="" the="" phenomena="" occurring="" in="" the="" furnace="" not="" only="" on="" the="" processes="" of="" slagging="" and="" formation="" of="" ht="" fouling="" but="" also="" on="" the="" nature="" of="" mt="" deposits="" covering="" the="" tubes="" in="" the="" convection="" part="" of="" the="" boiler.="" with="" accuracy="" sufficient="" for="" technical="" purposes,="" this="" effect="" can="" be="" determined="" computationally="" by="" the="" formulae="" (8.56)="" and="" (8.57).="" once="" the="" increased="" amounts="" of="" calcium="" and="" magnesium="" compounds="" are="" added="" to="" the="" combustion="" chamber,="" the="" b/a="" value="" (8.54)="" increases.="" as="" a="" result,="" the="" effectiveness="" number="" of="" the="" heat="" exchanger="" changes="" according="" to="" the="" equation="" (assuming="" the="" mean="" exponent="" for="" in-line="" and="" staggered="" tube="" banks)="" (8.59)="" this="" proves="" that="" as="" the="" amount="" of="" basic="" substances="" increases,="" the="" value="" of="" f="" will="" decrease.="" an="" additional="" factor="" lowering="" f="" is="" the="" enrichment="" of="" fly="" ash="" with="" very="" fine="" particles,="" such="" as="" cao="" resulting="" from="" calcination="" of="" calcium="" hydroxide="" (decrease="" of="" r0.03).="" sometimes="" the="" presence="" of="" sulfates="" and="" other="" cementitious="" compounds="" in="" loose="" powdery="" deposit="" can="" cause="" the="" formation="" of="" fouling="" of="" considerable="" strength.="" strengthening="" occurs="" after="" reaction="" with="" water="" that="" may="" occur="" in="" the="" boiler="" either="" as="" a="" result="" of="" atmospheric="" moisture="" condensation="" on="" a="" standstill="" and="" in="" case="" of="" inadequate="" surface="" cleaning="" of="" tubes="" with="" water.="" this="" phenomenon="" can="" make="" impossible="" the="" cleaning="" of="" heating="" surfaces="" by="" means="" of="" sootblowing.="" similarly,="" the="" lt="" deposits="" are="" formed="" at="" temperatures="" lower="" than="" the="" dew="" point="" temperature.="" introduction="" bill="" rehm,="" ...="" abdullah="" al-yami,="" in="" underbalanced="" drilling:="" limits="" and="" extremes,="" 2012="" 1.13.2="" mud="" displacement="" when="" pulling="" pipe="" underbalanced="" wells="" make="" hole="" fill="" up="" easy="" when="" tripping,="" but="" it="" is="" very="" different="" from="" a="" normal="" trip="" fill="" up.="" the="" following="" items="" are="" important="" when="" pulling="" out="" of="" the="" hole="" (poh):="" ="" if="" there="" is="" no="" permeability,="" the="" bottom-hole="" pressure="" could="" be="" kept="" at="" about="" the="" same="" pressure="" by="" adding="" enough="" fluid="" to="" compensate="" for="" drillpipe="" displacement="" in="" the="" wet="" part="" of="" the="" hole.="" ="" if="" there="" is="" reasonable="" fluid="" permeability="" and/or="" lost="" circulation="" zones,="" the="" fluid="" is="" going="" to="" seek="" its="" own="" level.="" nothing="" in="" the="" way="" of="" the="" drillpipe="" hole="" fill="" up="" will="" make="" a="" difference.="" this="" is="" a="" place="" where="" a="" mud="" cap="" might="" be="" used="" to="" keep="" the="" formation="" fluid="" from="" coming="" to="" the="" surface="" (see="" section="" 1.13.4="" mud="" cap="" or="" chapter="" 7,="" mud="" cap="" drilling="" in="" fractured="" formations).="" ="" if="" there="" is="" a="" danger="" of="" wellbore="" fluid="" or="" gas="" to="" the="" surface,="" fill="" up="" can="" be="" done="" on="" a="" normal="" drilling="" basis.="" the="" ideal="" solution="" would="" be="" a="" down-hole="" casing="" valve.="" the="" next="" best="" choice="" is="" the="" mud="" cap.="" it="" is="" a="" heavier,="" thicker="" column="" of="" mud="" placed="" at="" some="" distance="" downhole="" to="" overbalance="" the="" well="" and="" keep="" formation="" fluid="" from="" coming="" to="" the="" surface.="" advances="" in="" managed="" pressure="" drilling="" technologies="" m.rafiqul="" islam,="" m.enamul="" hossain,="" in="" drilling="" engineering,="" 2021="" 5.6.4="" candidate="" screening="" candidate="" screening="" is="" a="" filtering="" process="" to="" match="" the="" particular="" udt="" to="" the="" problem="" faced="" by="" the="" well="" section.="" a="" detailed="" screening="" allows="" the="" engineer="" to="" identify="" the="" right="" technique="" and,="" most="" importantly,="" the="" correct="" spread="" of="" equipment.="" the="" comparison="" below="" highlights="" a="" generic="" screening="" result="" for="" these="" two="" techniques.="" 5.6.4.1="" underbalanced="" drilling="" ="" ubd="" is="" an="" excellent="" candidate="" for="" depleted="" formations,="" especially="" when="" production="" enhancement="" is="" the="" target.="" ="" ubd="" is="" and="" has="" been="" applied="" in="" formations="" with="" the="" following="" characteristics:="" ="" depleted="" formations="" for="" production="" enhancement;="" ="" formation="" damage="" prevention;="" ="" storage="" or="" injector="" wells;="" ="" depleting="" nuisance="" zones,="" such="" as="" high-pressure,="" low-volume="" gas="" pockets="" in="" top-hole="" sections;="" ="" real-time="" formation="" evaluation="" (single="" point="" production="" test="" or="" drawing="" productivity="" index="" while="" drilling);="" ="" lost="" circulation="" zones;="" ="" tombstone="" rock="" drilling="" in="" intermediate="" hole="" section.="" 5.6.4.2="" managed="" pressure="" drilling="" ="" due="" to="" its="" zero="" influx="" policy,="" mpd="" can="" be="" applied="" in="" sections="" that="" are="" prone="" to="" lost="" circulation,="" areas="" where="" stuck="" pipe="" is="" an="" issue,="" or="" in="" hpht="" reservoirs="" to="" avoid="" npt,="" mainly="" in="" the="" form="" of="" high="" mw="" or="" ecds.="" ="" to="" date,="" 70%="" of="" mpd="" wells="" have="" needed="" ecd="" control="" to="" avoid="" reaching="" fracture="" gradient="" or="" creating="" drilling-induced="" fractures.="" therefore,="" most="" mpd="" today="" revolves="" around="" ecd="" or="" pseudo-mw="" control="" without="" increasing="" any="" solids="" in="" the="" mud="" to="" create="" the="" same="" effect="" of="" ecd="" as="" created="" by="" a="" weighted="" mud.="" ="" a="" few="" cases="" have="" also="" seen="" a="" reduction="" in="" casing="" strings="" by="" controlling="" ecd="" at="" the="" sandface.="" once="" the="" desired="" td="" is="" reached,="" the="" casing="" is="" landed="" to="" secure="" the="" section="" without="" adding="" any="" additional="" strings.="" ="" mpd="" has="" also="" seen="" a="" great="" value="" in="" hpht="" wells,="" where="" longer="" open="" holes="" are="" able="" to="" be="" drilled,="" which="" were="" not="" possible="" with="" the="" traditional="" way="" of="" increasing="" mw="" to="" control="" the="" formation="" pressure.="" in="" summary,="" ubd="" is="" primarily="" concerned="" with="" production="" enhancement="" from="" depleted="" reservoirs.="" mpd="" works="" with="" issues="" that="" are="" related="" to="" high="" mws="" and="" ecds="" that="" result="" in="" shorter="" wellbore="" length,="" challenging="" windows="" between="" pore="" and="" fracture="" gradient="" or="" areas="" where="" lost="" circulation="" is="" induced="" due="" to="" dilation="" of="" near-wellbore="" fractures.="" the="" bottom="" hole="" circulating="" pressure="" throughout="" an="" mpd="" operation="" remains="" slightly="" above="" the="" pore="" pressure.="" casing="" and="" pipeline="" corrosion="" george="" v.="" chilingar,="" ...="" ghazi="" d.="" al-qahtani,="" in="" the="" fundamentals="" of="" corrosion="" and="" scaling="" for="" petroleum="" &="" environmental="" engineers,="" 2008="" 5.2.6="" liners="" liners="" are="" the="" pipes="" that="" do="" not="" reach="" the="" surface,="" and="" are="" suspended="" from="" the="" bottom="" of="" the="" casing="" string="" above.="" usually,="" they="" are="" set="" to="" seal="" off="" troublesome="" sections="" of="" the="" well="" or="" through="" the="" producing="" zones="" for="" economic="" reasons.="" basic="" liner="" assemblies="" are="" shown="" in="" figure="" 5.2.="" they="" include="" drilling="" liner,="" production="" liner,="" tieback="" liner,="" scab="" liner,="" and="" scab="" tieback="" liner="" (brown-hughes="" co.,="" 1984).="" sign="" in="" to="" download="" full-size="" image="" figure="" 5.2.="" basic="" liner="" systems.="" (after="" brown-hughes="" co.,="" 1984)copyright="" ="" 1984="" 1.="" drilling="" liner:="" drilling="" liner="" is="" a="" section="" of="" casing="" that="" is="" suspended="" from="" the="" existing="" casing="" (surface="" or="" intermediate="" casing).="" in="" most="" cases,="" it="" extends="" downward="" into="" the="" openhole="" and="" overlaps="" the="" existing="" casing="" by="" 200="" to="" 400="" ft.="" it="" is="" used="" to="" isolate="" abnormal="" formation="" pressure,="" lost="" circulation="" zones,="" heaving="" shales="" and="" salt="" sections,="" and="" to="" permit="" drilling="" below="" these="" zones="" without="" having="" well="" problems.="" 2.="" production="" liner:="" production="" liner="" is="" run="" instead="" of="" full="" casing="" to="" provide="" isolation="" across="" the="" production="" or="" injection="" zones.="" in="" this="" case,="" intermediate="" casing="" or="" drilling="" liner="" becomes="" part="" of="" the="" completion="" string.="" 3.="" tieback="" liner:="" tieback="" liner="" is="" a="" section="" of="" casing="" extending="" upwards="" from="" the="" top="" of="" the="" existing="" liner="" to="" the="" surface.="" this="" pipe="" is="" connected="" to="" the="" top="" of="" liner="" (figure="" 5.2b)="" with="" a="" specially="" designed="" connector.="" production="" liner="" with="" tieback="" liner="" assembly="" is="" most="" advantageous="" when="" exploratory="" drilling="" below="" the="" productive="" interval="" is="" planned.="" it="" also="" gives="" rise="" to="" low="" hanging="" weights="" in="" the="" upper="" part="" of="" the="" well.="" 4.="" scab="" liner:="" scab="" liner="" is="" a="" section="" of="" casing="" used="" to="" repair="" existing="" damaged="" casing.="" it="" may="" be="" cemented="" or="" sealed="" with="" packers="" at="" the="" top="" and="" bottom="" (figure="" 5.2c).="" 5.="" scab="" tieback="" liner:="" scab="" tieback="" liner="" is="" a="" section="" of="" casing="" extending="" upward="" from="" the="" existing="" liner,="" but="" which="" does="" not="" reach="" the="" surface="" and="" is="" normally="" cemented="" in="" place.="" scab="" tieback="" liners="" are="" commonly="" used="" with="" cemented="" heavy="" wall="" casing="" to="" isolate="" salt="" sections="" in="" deeper="" portions="" of="" the="" well.="" possible="" leaks="" across="" the="" hanger="" and="" the="" difficulty="" in="" obtaining="" a="" good="" primary="" cement="" job="" due="" to="" the="" narrow="" annulus="" must="" be="" taken="" into="" consideration.="" recommended="" publications="" publication="" cover="" applied="" thermal="" engineering="" journal="" publication="" cover="" chemical="" engineering="" research="" and="" design="" journal="" publication="" cover="" international="" journal="" of="" thermal="" sciences="" journal="" publication="" cover="" building="" and="" environment="" journal="" elsevier="" logo="" about="" sciencedirect="" remote="" access="" shopping="" cart="" advertise="" contact="" and="" support="" terms="" and="" conditions="" privacy="" policy="" we="" use="" cookies="" to="" help="" provide="" and="" enhance="" our="" service="" and="" tailor="" content="" and="" ads.="" by="" continuing="" you="" agree="" to="" the="" use="" of="" cookies.="" copyright="" ="" 2021="" elsevier="" b.v.="" or="" its="" licensors="" or="" contributors.="" sciencedirect="" ="" is="" a="" registered="" trademark="" of="" elsevier="" b.v.="" relx="" group="" home="" page="">