Well-Bore Structure (Drilling and Completions)

David A. Simpson P.Due east. , in Practical Onshore Gas Field Engineering, 2017

ii.7.3 Perforating

For a conventional well, we set heavy-wall product casing across the target germination and then sheathe it in cement to make certain that no reservoir fluids can go into the well-diameter. This is useful for keeping explosive liquids and gases away from the rig floor, but information technology is ineffective for production. To make a cased well bachelor for production, you have to make holes in the casing and cement. Big holes. Many of them. Deep. Deeper than you lot could get with a drill fleck. We apply explosive charges to brand them.

The goal of perforating is to provide a make clean flow-channel between the producing formation and the well-diameter while causing minimal damage to the producing formation. The ultimate test of the effectiveness of a perforating job is well productivity. Productivity depends on perforation length, shot density, athwart phasing (i.e., the direction that the holes become relative to each other), perforation diameter, and how much droppings is left behind. Each of these dependencies is further dependent on external factors similar the germination characteristics and the importance of each changes from well to well.

2.7.3.one Gun types

Perforating guns are usually made up of a number of shaped charges, but there are some bullet guns for specialized applications. At that place are many types of shaped-charge guns that can be used and they fall into about 3 categories:

•

Retrievable hollow gun—the charge is secured in a steel tube which is sealed confronting hydrostatic pressure. When the accuse blows, the tube can expand and sometimes get stuck in the well and accept to exist milled out. This is rare and these guns leave minimal droppings in the well.

•

Nonretrievable (expendable) gun—fabricated up of individual sealed cases, each containing a charge. Sealed cases are fabricated of a frangible material such as aluminum, ceramic, or cast iron. The case is blown into small pieces that remain in the well.

•

Semiexpendable gun—charges in sealed cases are secured on a retrievable wire carrier or metal bar. This configuration reduces the debris left in the well and increases the ruggedness of the gun.

2.vii.3.2 Conveyance methods

We deploy perforating guns either with a wireline or on a tubing (or coiled tubing) cord. When wireline deployment is used, information technology tin either be done before or later on the installation of tubing. "Thru casing" jobs are run before the tubing is installed and allow for the largest perforating gun that tin fit through the casing. "Through tubing" jobs are run through the tubing and out the end and are express in the diameter of perforating gun that tin exist run, and this method allows the casing in a higher place the gun to be isolated with inflatable packers to increase the forcefulness of the smash. Since it is ineffective to push on a rope, perforating in horizontal and high-bending wells oft cannot be done with wireline-conveyed deployment. The weight of the gun is also express by the carrying capacity of the wireline.

Tubing-conveyed perforating allows casing-conveyed gun sizes to exist used with considerably improved control of placement, isolation from the casing above the tool, larger perforated intervals can be shot considering the tubing has much more than strength in tension than a wireline, better isolation of reservoir pressure from the surface, and you can push tubing into extended laterals. The downside of tubing-conveyed perforating is that it is more expensive to pull the tubing string than to spool upwardly a wireline. Using coiled tubing has all of the benefits of both wireline and tubing-conveyed and is condign very common.

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Coiled Tubing Well Control

Howard Crumpton , in Well Command for Completions and Interventions, 2018

10.vi.seven Running perforating guns on coiled tubing

Running perforating guns on coiled tubing has a number of advantages:

•

Live well gun running is simple and condom.

•

A higher underbalance pressure tin can be used (by comparison with wireline).

•

The coil can be used to introduce an underbalance cushion prior to gun detonation.

•

Coil enables guns to exist come across high angle and horizontal wells.

•

Gun deployment systems enable long guns to be come across live wells—the potential exists to perforate long intervals in a single run, and with underbalance.

•

Scroll tubing trip times are faster that using jointed pipage.

Operational and well command considerations when perforating with coiled tubing include:

•

Pressure control equipment—for most perforating operations the standard pressure level command equipment is adequate. To operate in a alive well, the riser must be long enough to accommodate the perforating guns. If there is a requirement to perforate an interval that is longer than the riser length available, multiple perforating runs can be carried out. Alternatively, a live well gun deployment organization can be used.

•

Gun deployment systems allow multiple gun sections to be installed in a well where the overall length of the gun is longer than the riser length available. Gun sections are joined using special connectors. Each connection is made within the pressurized riser using specially designed deployment BOPs.

•

Firing mechanism:

•

Electrical firing—to fire perforating guns electrically requires an electric cable inside the coiled tubing, and a firing caput as part of the BHA. An electric cable has the boosted advantage of enabling GR/CCL to exist run with the roll for accurate depth correlation, overcoming the limitations of mechanical depth measurement.

•

Pressure activated firing—tubing conveyed guns can be fired using pressure activated firing heads. Near accept an integral fourth dimension delay with a predetermined elapsing between the application of pressure level and gun detonation. Wellsite supervisors demand to know how the firing head selected for any perforating operation works. Insufficient cognition could exist fatal.

•

Depth control:

•

Roll tubing depth measurement is often rudimentary. The counters used on the injector head and level wind arm are prone to slippage, and they are not able to place a perforating gun on depth with enough accurateness. There will often exist something in the well that can be used to ostend depth—east.k., a difficult tag against a span plug.

•

If an electrical firing head is used, i.eastward., the coil is equipped with an internal electrical cable, and then GR/CCL depth correlation enables authentic depth determination.

•

Perforating loose, unconsolidated sandstone formations risks sand entering the wellbore and sticking the gun. This risk increases with increasing underbalance. The employ of loftier shot density "big-pigsty" charges likewise increases risk.

Coiled tubing perforating incident: Case history. 10

In Jan 2010, coiled tubing perforating operations were taking place on a jack-upwards rig in the Dutch sector of the Northward Sea. A force per unit area activated firing head with a 30 minute time filibuster was in use. As the guns were run to depth, nitrogen was circulated through the coil tubing via a port above the firing head. Once the guns had been positioned at the right firing depth, a ball was pumped/dropped through the coiled tubing, to isolate the circulating ports and allow reel pressure to exist increased, activating the firing head. Activation of the firing head should have been confirmed by reestablishing apportionment through the coiled tubing. This was non done. At the surface, the crew observed a pressure spike. Mistakenly thinking the guns had been activated, they stopped pumping and bled off pressure. Crucially, they did not attempt to circulate, nor did they ostend the volume of nitrogen pumped was sufficient to seat the dropped ball, i.e., the estimate volume of the whorl. The crew, assuming the gun had fired, recovered it to surface.

After closing in the well, the coiffure began to depressurize the riser. As the riser was beingness depressurized, the coiled tubing operator in the control motel noticed that pressure in the coil had not dropped along with the riser force per unit area as expected, and equally should have been the case, had the firing caput activated and the circulation path reestablished. Moreover, the differential pressure between that trapped in the coil and the rapidly depressurizing riser created enough differential pressure to initiate the fourth dimension delay. Realizing that the time filibuster sequence had begun, the area around the pressure command equipment was evacuated. A short time later the guns fired, destroying the riser and BOP. Remarkably, no one was harmed.

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Perforating

Wan Renpu , in Advanced Well Completion Engineering (Third Edition), 2011

Horizontal Well Perforating Technology

The matching techniques and theory that are related to horizontal wells have been profoundly advanced since the application of horizontal wells to oil field evolution began in the early 1980s. Now, long-interval deep-well directional perforating, combined perforating and testing operation of horizontal wells, horizontal well reperforating, limited-entry fracturing perforating of horizontal wells, nitrogen gas extreme overbalance perforating of horizontal wells, and then on, take all been achieved. Horizontal well perforating has become a conventional perforating operation.

Horizontal wells with formations that exercise non hands slough prefer perforated completion at present in club to finer preclude gas and water coning and to brand split-zone production and operation convenient. The perforating gun used in a horizontal well is generally conveyed on tubing or coiled tubing. The downhole perforating assembly of a horizontal well includes generally a locator sub, detonating device, underbalance accessories, packer, oriented perforating gun, centralizer, and ball guide shoe.

A horizontal well has a long perforating interval and a large skip altitude; thus, the detonation safe of a perforating gun and the detonating quality should be emphatically considered, and several detonators are by and large used. Pressure level detonation is ordinarily used for perforating in horizontal wells. On the basis of different goals and usage, information technology tin be tubing pressurization detonation, annulus pressurization detonation, pressure opening device plus pressure difference (filibuster) detonation, opening gun plus pressure (delay) detonation, integrated pressure level (delay) detonation opening device, or bamboozle detonation-transmitting device, and so on.

The baffle detonation-transmitting technique is shown in Figure 6-13. Both ends of the interbed gun are plugged by using a baffle fire workpiece. The detonation energy of the perforating gun is reliably transmitted to the perforating gun below the interbed gun through the bamboozle detonation-transmitting device. Both ends of the interbed gun after explosion are in a sealed state, thus preventing well fluid from entering.

Figure 6-13. Baffle detonation-transmitting device.

The perforating guns are pulled to the wellhead afterwards perforating. The pressure in the interbed gun tin can be relieved safely and reliably by the pressure relief valve of the baffle detonation-transmitting device. This technique has the post-obit advantages:

1.

Suitable for the diverse perforating operations with gun torso

2.

Reliable for transmitting detonation energy with stable detonation manual, resistance to pressure of 100   MPa, and reliable sealing

3.

No sullage in the interbed gun, no platform and bounding main contamination, and no need for cleaning the interbed gun, which is used repeatedly

4.

Reliably releasing the gas in the interbed gun by the pressure relief valve at adapter, safely removing the gun, making gun removal faster, and reducing labor intensity

5.

Safe and reliable detonation transmitting from top to bottom or from lesser to top

This technique has been widely applied, and good economic and social benefit has been obtained. Its application will greatly reduce ecology pollution and raise operational prophylactic and efficiency.

The other key to horizontal well perforating lies in selecting an appropriate perforating gun. The perforating gun should exist safely run to target and pulled out safely, which requires no plastic deformation of the perforating gun during passage through the well section of curvature, requires smooth rotating of the charge carrier in the gun body, and requires little deformation of the gun body later perforating without tearing at perforations. Therefore, the perforating gun made of seamless steel pipe, which is candy by using special technology including heat treatment, is selected depending on actual formation weather condition. After perforating, the burr pinnacle should non exceed 3 mm, and the maximum expansion should not exceed 5 mm.

On the footing of orientation, horizontal well perforating includes circumferential perforating (360°) and low-side perforating (180° and 120°), every bit shown in Figure 6-14. The orientation selection is mainly dependent on the caste of hardness of formation. In general, under the condition of unconsolidated reservoir, a perforating orientation of 120° to 180° is adopted in order to avoid wellbore plugging due to dropping of cuttings of the upper part of the horizontal section later on perforating.

Figure six-14. Perforating orientation for horizontal well.

The horizontal well perforating orientation is dependent on the orientation of the perforating gun of the horizontal well. The gravitational orientation of the perforating gun includes external orientation and internal orientation. The external orientation adopts the blades melded to the gun body, and the perforating orientation is achieved by the integral rotation of perforating guns under the condition of eccentric gravity nether the unbalanced friction resistance between blade and borehole wall in combination with a rotation sub. The internal orientation adopts the eccentric setting of accuse carrier in the gun body, and the perforating orientation of each gun is achieved past the rotation of charge carrier under the status of eccentric gravity in combination with an eccentric back up. The internal orientation technique is in mutual use in Red china due to its loftier accuracy, effectiveness, ease of detection, and enabling the installation of a larger perforating gun. The internal orientation includes eccentric rotation type and weight rotation blazon.

At present, the horizontal well oriented perforating arrangement (HOPS) developed by Baker Hughes likewise adopts the internal orientation of weight rotation type (Effigy 6-xv). The orientation of whatsoever angle tin exist achieved by using a rotation sub and has a degree of accurateness of ±five°.

Figure 6-fifteen. Oriented perforating system for horizontal well.

A large-calibration horizontal perforating using the HOPS organization was accomplished in the Due north Sea in 2002. The well had a horizontal section length of 2246 m and total perforating length of 1490 m. It adopted a casing of Φ177.8 mm (vii in.) and a perforation density of 16 shots/m. Tubing-conveyed perforating guns of Φ114 mm were adopted. Each gun had a length of vii.eleven m (28   ft). The phase of 0 to 180°, which is perpendicular to the minimum principal stress, was adopted in order to achieve sand control (Effigy 6-xvi). A full of 23180 low-debris deep-penetration perforating charges and 188 rotation subs were installed.

Figure half dozen-sixteen. Oriented perforating in horizontal well by using HOPS system.

Horizontal wells are existence increasingly applied in People's republic of china due to their product effectiveness, which is ameliorate than that of directly wells. Thus the perforated completion technology of horizontal wells is also existence developed along with the application of horizontal wells and gradually is becoming the main ways of horizontal well completion. For instance, wells including TZ sixteen-7, TZ sixteen-12, TZ four-vii, H23, and TZ 404 H have all adopted perforated completion. The diverse perforation strings of a horizontal well have been designed, horizontal well perforating tools that are advisable to a long horizontal section, deep well, and medium curvature and include a perforating gun made of seamless steel pipe, bidirectional delay pressure detonator, and ball guide shoe have been developed, and the corresponding technological measures have been designed. They have been successfully practical in high-temperature high-force per unit area horizontal wells, and good technological results have been obtained.

The perforation string of the TZ sixteen-7 well is shown in Figure 6-17. The combined string of Φ88.9 mm drill piping in the upper part and Φ73 mm tubing in the lower role is used for conveying the perforating gun. The cord structure includes guide, detonator, perforating gun, bidirectional detonator, perforating gun, detonator, prophylactic gun, Φ73 mm tubing, locator sub, Φ73 mm tubing, and Φ88.ix mm drill pipe to the wellhead.

Effigy 6-17. TZ xvi-7 perforated completion cord for horizontal well.

In recent years, coiled tubing-conveyed perforating technology has been widely applied in horizontal or extended attain wells due to its safe and convenient operation and specific reservoir-protecting action, and and so on.

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Completion, Reservoir Drilling, Workover, and Packer Fluids*

Ryen Caenn , ... George R. Gray , in Limerick and Backdrop of Drilling and Completion Fluids (Sixth Edition), 2011

When Gun Perforating

The harm caused past gun perforating with conventional muds in the hole has been recognized for some time (Allen and Atterbury 1958). Even if a well is perforated with a completely nondamaging fluid, productivity is decreased by the germination of a zone of crushed rock around the perforation tunnel (see Figure 10.eighteen). If the productivity of this zone is further reduced by mud solids or filtrate, the productivity of the well will be reduced severely. Based on experimental data, Klotz et a1. (1974a) have calculated loss of well productivity resulting both from formation damage by mud solids and filtrate while drilling and from impairment to the zone around the tunnel. Figure 10.19 shows that if a well is perforated with a completely nondamaging fluid and if the permeability of the formation has not been impaired while drilling (kr = 100%) permeability of the crushed zone (kp ) is 20% of the original rock permeability, and productivity is fourscore% of potential. If the permeability of the formation has been impaired during drilling, productivity may be reduced to equally low as 20% of potential, depending on the value of grandf and the depth of invasion. Effigy 10.xx shows that if the well is perforated with a dissentious fluid in the hole, the permeability of the crushed zone may be reduced to as footling as 5% of the original permeability, and the maximum productivity that can then be expected (even if there is no impairment during drilling) is 45% of potential. These results show that perforating with a nondamaging fluid in the pigsty is of the utmost importance.

Effigy 10.18. Schematic representation of a gun perforation, showing zone of crushed rock around tunnel.

 From Klotz et al. (1974a) . Copyright 1974 by SPE-A1ME.

Figure x.19. Effect of damage by mud while drilling on well productivity when perforated with a nondamaging fluid. chiliadp is permeability of crushed zone around perforation tunnel equally a percentage of initial permeability.

 From Klotz et al. (1974a) . Copyright 1974 by SPE-A1ME.

Figure x.xx. Effect of mud damage while drilling on well productivity when perforated with a damaging fluid.

 From Klotz et al. (1974a) . Copyright 1974 by SPE-AIME.

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Advances in Cardinal Applied science Technologies for Re-exploration

Xianzheng Zhao , ... Xiugang Pu , in Re-exploration Programs for Petroleum-Rich Sags in Rift Basins, 2018

Fast and drillable bridge plug completion

Perforate and fracture the first stage. Run the perforating gun and a bridge plug by a cable pump to the 2d stage, perforate the 2d stage after setting and releasing the plug, and fracture the section later perforating and running out of the perforating gun and the setting tool. Repeat the procedure until finishing all stages. Drill out all plugs on the final run. At nowadays, bachelor bridge plugs include drillable and acid-soluble ones, which should be dissolved at the best time. The advantages of this applied science include plug setting and perforation on one trip, no need of special fracturing string, pumping fracturing fluid into casing string, low friction, large displacement, but loftier standards for setting and perforating tools. This completion method has been applied to the Eagle Ford shale gas wells in the U.s.a. and the Jiaoshiba shale gas wells in China, where 15–22 stages take been fractured in a well.

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Completion, Workover, Packer, and Reservoir Drilling Fluids

Ryen Caenn , ... George R. , in Composition and Properties of Drilling and Completion Fluids (Seventh Edition), 2017

An Oil-in-Water Emulsion for Gun Perforating

Earlier, the importance of using a nondamaging fluid when gun perforating overbalanced was emphasized. Priest and Morgan (1957) and Priest and Allen (1958) developed a solids-free emulsion specifically for this purpose. Typically, it consists of 40% oil emulsified in sodium chloride or calcium chloride brine.

The oil phase is either kerosene or carbon tetrachloride, or mixtures of the same, depending on the density required. The maximum density is 12.v   lb/gal (ane.fifty SG). The emulsion is stable enough to provide filtration control for 24   hours. To minimize costs, simply a slug of emulsion is pumped into the well, and spotted reverse the interval to be perforated, the density having previously been adjusted and so that it maintains this location. Results from the field showed that the emulsion caused no impairment either when perforating or during workover jobs with exposed perforations

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Well Impale, Kick Detection, and Well Shut-In

Howard Crumpton , in Well Control for Completions and Interventions, 2018

7.thirteen.4 Tubing conveyed perforation guns in an overbalanced well

Perforating with underbalance is more often than not preferred for well functioning reasons. Withal, when tubing conveyed perforating guns (TCP) are used, cost and operational complexity are both reduced if perforating takes place with kill weight fluid filling the well. Withal, fifty-fifty with an overbalance fluid in the well, the gamble of a kick cannot be overlooked ( Fig. 7.thirty). The following should be considered:

Figure 7.30. Typical piping deployed tubing conveyed perforation configuration for overbalanced perforation.
•

If the guns are force per unit area activated, use a time delay firing head to enable the gun activation pressure to be bled-off before the gun fires. If the wellbore force per unit area is high when the guns burn down, there is a risk of fracturing the formation. In addition, formation damage will exist considerably worse because of the additional overbalance.

•

Make sure a suitable LCM pill is circulated into the well and spotted in a higher place the perforations.

•

If at that place is a boot because of losses, or a higher than expected reservoir pressure, then the annular bag or pipage rams must be airtight.

•

BOP pipe rams volition non seal on spent (fired) perforating guns. Many pipe conveyed gun assemblies are long—in the example of horizontal wells many thousands of feet. If guns are straddling the BOP when the well kicks, they will take to be sheared and dropped and then that the blind rams can be closed, making the well safe.

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Horizontal well multistage completion techniques

Hoss Belyadi , ... Fatemeh Belyadi , in Hydraulic Fracturing in Unconventional Reservoirs (2nd Edition), 2019

Cluster spacing

There are various clusters in each frac stage. A cluster is referred to as a perforating gun. If at that place are five clusters in 1 frac phase, there are five perforation guns in that stage that are usually evenly distributed (geometric pattern). The industry average for the number of guns (eastward.g., clusters) in the anarchistic reservoirs is anywhere betwixt 3 and 20 clusters that are as spaced in each stage. For example, if six clusters are used for a 300′ frac phase, the cluster spacing is 50′. The industry average for cluster spacing is 20′–lx′. Every operator has its own theory regarding the number of clusters and holes in a frac stage. The major deciding factor in choosing the number of clusters is formation permeability, GIP, and perforation efficiency. A general rule of thumb is that if the germination permeability is higher than usual, fewer clusters will be needed. In contrast, if the formation permeability is lower, more clusters will exist necessary. The goal is to achieve the maximum surface area between clusters. In addition, if GIP in a item area is not significant, fewer clusters and stages will be needed to release the hydrocarbon.

Some operating companies believe that the spacing between clusters needs to be minimized to gain the most surface expanse out of each zone. On the other hand, others believe that a lower number of clusters are necessary to achieve longer fracture networks by forcing the hydraulic fracturing energy to go to a limited number of clusters. Every operator justifies its theory with its production results. Having shorter cluster-to-cluster spacing has shown to maximize the product consequence in sure areas. Hydraulic fracturing operation in shorter cluster-to-cluster spacing has sometimes shown to be more difficult due to competing fractures or communication between clusters.

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Measures for Putting a Well into Production

Wan Renpu , in Advanced Well Completion Engineering science (Third Edition), 2011

Combined Loftier-Energy Gas Fracturing and Perforating

The perforating charge carriage in which perforating charges and fracturing propellant charges are rammed is installed in the perforating gun body. The perforating gun is run on tubing, and a bar is dropped for detonating. Perforating charges first form perforations at reservoir interval. The high-temperature high-pressure gas that is generated by delayed combustion of propellant charges will enlarge and deepen the perforations upwardly to 1–two m, and multiple fractures may be formed along the perforations. The range of fractures is up to 2–8 m. This technique has the following features:

one.

The energy utilization factor of loftier-temperature high-force per unit area gas is increased. When high-free energy gas fracturing is adopted, the fracturing charges are burned in the casing, and only a small quantity of gas may enter the reservoir through perforations. When combined perforating and high-energy gas fracturing are adopted, the most gas generated by propellant combustion may act on the reservoir through perforations; thus, the energy utilization factor of the gas generated by propellant combustion may be profoundly increased.

2.

Combined loftier-free energy gas fracturing and perforating simplifies the operations. Perforating (reperforating) and fracturing tin be performed once, so that the cost is reduced.

3.

When high-temperature high-pressure gas generated by propellant combustion is projected into the reservoir at high speed, the perforations are scoured and deepened. The effectiveness is much higher than that of exclusive high-free energy gas fracturing.

four.

Simultaneous multi-interval operations can be achieved.

When combined high-energy gas fracturing and perforating is adopted, the propellant selected should be insensitive to explosions, and the surface of propellant should be passivated.

The human relationship between combustion rate and pressure for missile propellant and unmarried-base propellant is shown in Figure 8-63. The sensitivity tests indicate that the single-base of operations propellant of nitrocellulose has a lower sensitivity to explosions; thus, nitrocellulose is selected.

Figure 8-63. Human relationship between combustion rate and pressure for missile propellant and unmarried-base of operations propellant.

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Offshore Oil and Gas Drilling Applied science and Equipment

Huacan Fang , Menglan Duan , in Offshore Functioning Facilities, 2014

ii.5.i.iii Perforating Process Blueprint

one.

Selection of perforating modes

a.

Existing perforating modes

i.

Cable perforation

This is a method where the casing perforating gun is run down by the cable, the casing pup joint on the top of the reservoir is used to position the perforating depth, and the perforating gun is fired by the electric detonators to shoot through the oil and gas production layer, which can come across the requirements of high-density, deep penetration, large aperture perforation, and multi-layer perforation.

2.

Tubing conveyed perforation

This is a new perforating method where the perforating gun is conveyed to the perforating horizon by the tubing. This method in which large bore perforating guns are used is suitable for high-pressure oil and gas wells, and highly deviated and horizontal wells.

3.

Through-tubing perforation

This method later completing the adjacent production cord, installing wellhead Christmas tree and product systems, plugging device, is to install the lubricator on the wellhead Christmas tree and cable sealing device, and cable down into the perforating gun from the tube perforating reservoir; the structure of the perforating gun is shown in Figure 2-91. This method is condom and suitable for loftier-pressure oil and gas wells, and a well can be put into product immediately later on perforation.

Figure two-81. Φ476.25 mm wellhead and wellhead devices of floating drilling platform.

Effigy 2-82. Drilling procedure in surface casing of floating drilling platform.

FIGURE 2-83. Casing head installment and welding of self-elevating drilling platform.

FIGURE two-84. Wellhead and wellhead devices of self-elevating drilling platform used in China.

FIGURE two-85. Assembly of casing hanger when down the technical casing in the floating drilling platform.

Effigy 2-86. Associates of drill pipage cement head in the floating drilling platform when down casing.

FIGURE 2-87. Installment of Φ339.73 mm technical casing in the wellhead.

Figure 2-88. Wellhead devices of Φ339.73 mm technical casing in cocky-elevating drilling platform.

FIGURE 2-89. Operation process of oil-string casing in floating drilling platform.

FIGURE two-ninety. Wellhead devices of Φ244.48 mm oil-string casing in self-elevating drilling platform.

FIGURE 2-91. Structure of perforating gun for the method of through-tubing perforation.
iv.

Through-tubing extending perforation

The departure between the through-tubing perforation and through-tubing extending perforation is that the perforating gun is in a vertical land when it is run downward, but it is in a horizontal land afterwards reaching the perforating horizon and turns into a large diameter perforating gun.

You tin select the perforation modes with the reference to Tabular array 2-8.

Table 2-eight. Comparing between Several Perforating Methods

Perforating Methods Cable Perforation Tubing Conveyed Perforation Through-Tubing Perforation Through-Tubing Extending Perforation
Diameter of guns (mm) 73∼177.8 35∼54 73∼177.viii 42.9
Styles of bullet Deep penetration and large diameter Deep penetration Deep penetration and large diameter Deep penetration
Weight of bullet (thou) 15∼66 1.8∼17 15∼66 22
Density of holes (hole/m) thirteen∼39 13∼xix 13∼46 13
Depth of holes (mm) 400∼800 146∼615 400∼800 678
Bore of holes (mm) 7.1∼31.iii 5.four∼14.5 7.one∼31.3
Phase (∘) 120,90,lx,45,thirty lxxx,ninety,sixty,0 120,ninety,72,60, 51.4,45,30,twenty 180
Range of negative pressure Tin can not be negative pressure Can be controlled or isobaric Meets the requirements of negative pressure Can be controlled or isobaric
Adaptive depth of wells Diameters of casing pipes range from 114.3∼245mm, vertical wells, deviated wells within. Diameters of pipelines ≥ 60.3mm and diameters of casing pipes ≤ 245mm, vertical wells, deviated wells inside. Diameters of cased tubing range from 114.3∼245mm, vertical, deviated, and horizontal wells. Diameters of pipelines range from sixty.3∼114.3 mm, vertical wells, deviated wells within.
Range of application Ordinary wells Production wells, recharging wells Ordinary, loftier-pressure oil and gas wells; sand, low permeability, and difficult wells Production wells, recharging wells
Perforating result Perforating injury volition bear on the product capacity. The small aperture and lower depth volition perchance partly affect the production chapters. Flushing of the holes and loftier production chapters. The discontinuity is minor will perhaps partly touch the producing chapters.
ii.

Pick of perforating technology

a.

Styles of perforating technology

i.

Overbalanced perforating technology

The germination is shot through when the pressure of the completion fluid in the wellbore is higher than that in the formation; this is called an overbalanced perforating technology.

ii.

Underbalanced perforating technology

The formation is shot through when the pressure of the completion fluid in the wellbore is lower than that in the formation; this is called underbalanced perforating applied science. Underbalanced perforation tin eliminate the perforating fluid in the formation, and the perforation tunnel can be made make clean again to build a clean smooth flow aqueduct of oil and gas, which is the reason this applied science has been widely used. Usually it is used through the tubing conveyed perforation and through-tubing perforating method.

three.

Conclusion of the perforating negative pressure level

There are many sandstone reservoirs in the offshore oil and gas fields in China, and they are often divided into nondense formations and dense formations. A larger negative pressure can be selected in the situation every bit the former will not have sand afterward perforation; the latter has sand product hands after perforation, a reason the negative pressure should exist selected reasonably for that blazon of germination.

a.

Determination of the minimum perforating negative force per unit area

The minimum perforating negative pressure tin exist determined by the following equations for the nondense formation and the dense formation:

Oil reservoirs:

(ii-41) P min = 6.89 × iii.5 K 0.37

Gas reservoirs:

(2-42) P min = 2.v Grand 0.17

where K germination permeability and Pmin is the minimum perforating negative pressure, MPa.
b.

Determination of the maximum perforating negative pressure

The fourscore% compressive strength of the casing pipe (50% compressive strength of the quondam casing pipe), or lxxx% working pressure is selected as the maximum perforating negative pressure for the dense formation. The maximum perforating negative pressure can be adamant by the following equations for the nondense formation.

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https://world wide web.sciencedirect.com/science/article/pii/B9780123969774000020