Forming Perturbed In-Line Perforations

The present disclosure relates to forming perforations in oil and gas wells, and geothermal and CO2 injection (CCS) wells.

In the oil and gas industry, perforation jobs are performed across the pay zone to create a flow path from the formation into the wellbore. Perforation jobs can be performed using downhole perforating tools that include a perforation gun, an abrasive jet perforating tool, or similar type of tool. A perforating gun generally holds several explosive-shaped charges. The shaped charges can be configured to focus the explosive energy in a specific direction and create perforations through the casing and cement, penetrating into the surrounding formation. An abrasive jet perforating tool deploys high-pressure abrasive fluid jets to cut through the casing, cement and into the surrounding formations. In some cases, one-third of perforation clusters do not yield oil or gas. Knowing where to appropriately place perforations, determining the hydraulic fracturing stages and achieving desired perforation geometry still remains a challenge for the oil and gas industry.

The present disclosure describes methods, devices, systems and techniques for forming perturbed in-line perforations.

In an example implementation, a bottom hole assembly includes a downhole conveyance that is extendable from a terranean surface, through a wellbore, and to a subterranean formation; and a perforating tool configured to couple to the downhole conveyance and create a perforation cluster in the subterranean formation. The perforation cluster includes perforations arranged along a longitudinal direction of the wellbore. The perforations include one or more first perforations extending along a first azimuthal direction, one or more second perforations extending along a second azimuthal direction at a first offset angle with respective to the first azimuthal direction, and one or more third perforations extending along a third azimuthal direction at a second offset angle with respective to the first azimuthal direction. The one or more second perforations and the one or more third perforations are alternative with each other along the longitudinal direction of the wellbore.

In an aspect combinable with the example implementation, the one or more second perforations are even-numbered perforations, and the one or more third perforations are odd-numbered perforations.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angle and the second offset angle range between about 0 degree and about 25 degrees.

In another aspect combinable with one, some, or all of the previous aspects, at least one of the second azimuthal direction or the third azimuthal direction is different than the first azimuthal direction.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angle is equal in magnitude and opposite in sign to the second offset angle.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angle is about −10 degrees, and the second offset angle is about +10 degrees.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angle is unequal in magnitude and opposite in sign to the second offset angle.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angle is about −10 degrees, and the second offset angle is about +25 degrees.

In another aspect combinable with one, some, or all of the previous aspects, the perforating tool includes shaped charges, detonating directions of the shaped charges being phased at azimuths smaller than about 60 degrees.

In another aspect combinable with one, some, or all of the previous aspects, the perforation cluster includes 6 perforations within a foot.

In another aspect combinable with one, some, or all of the previous aspects, the perforating tool includes a high-pressure coiled tubing jetting tool, a laser tool, or an abrasive jet perforating tool.

In another example implementation, a bottom hole assembly includes a downhole conveyance that is extendable from a terranean surface, through a wellbore, and to a subterranean formation; and a perforating tool configured to couple to the downhole conveyance and create a perforation cluster in the subterranean formation. The perforation cluster includes perforations arranged along a longitudinal direction of the wellbore. The perforations include one or more first perforations extending along a first azimuthal direction, second perforations extending along second azimuthal directions at first offset angles with respective to the first azimuthal direction, and third perforations extending along third azimuthal directions at second offset angles with respective to the first azimuthal direction. The first offset angles are opposite to the second offset angles in sign, and at least two of the second azimuthal directions are different from each other.

In an aspect combinable with the example implementation, the second perforations and the third perforations are alternative with each other along the longitudinal direction of the wellbore.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angles and the second offset angles are between about 0 degree and about 25 degrees.

In another aspect combinable with one, some, or all of the previous aspects, at least two of the third azimuthal directions are different from each other.

In another aspect combinable with one, some, or all of the previous aspects, each of the perforations extends along a unique direction.

In another aspect combinable with one, some, or all of the previous aspects, the perforating tool includes a high-pressure coiled tubing jetting tool, a laser tool, or an abrasive jet perforating tool.

In another example implementation, a method to form a perforation cluster includes positioning a perforating tool adjacent a subterranean formation within a wellbore; and operating the perforating tool to form a perforation cluster in the subterranean formation. The perforation cluster includes perforations arranged along a longitudinal direction of the wellbore. The perforations include one or more first perforations extending along a first azimuthal direction, one or more second perforations extending along a azimuthal second azimuthal direction at a first offset angle with respective to the first azimuthal direction, and one or more third perforations extending along a third azimuthal direction at a second offset angle with respective to the first azimuthal direction. The first offset angle is opposite to the second offset angle in sign.

In an aspect combinable with the example implementation, the first offset angle and the second offset angle are between about 0 degree and about 25 degrees.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angle is equal to the second offset angle in magnitude.

In another aspect combinable with one, some, or all of the previous aspects, the first offset angle is about −10 degrees, and the second offset angle is about +10 degrees.

In another aspect combinable with one, some, or all of the previous aspects, the perforation cluster includes 6 perforations within a foot.

In another aspect combinable with one, some, or all of the previous aspects, operating the perforating tool includes operating a high-pressure coiled tubing jetting tool, a laser tool, or an abrasive jet perforating tool.

In another aspect combinable with one, some, or all of the previous aspects, the perforations include a first set of in-line perturbed perforations arranged along a first longitudinal direction of the wellbore; and a second set of in-line perturbed perforations arranged along a second longitudinal direction of the wellbore.

In another aspect combinable with one, some, or all of the previous aspects, the first longitudinal direction is vertical at an azimuth of 0 degrees.

In another aspect combinable with one, some, or all of the previous aspects, the second longitudinal direction is horizontal at an azimuth of 90 degrees.

In another aspect combinable with one, some, or all of the previous aspects, each of the first and second sets of in-line perturbed perforations includes at least 6 perforations.

The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

It is to be understood that the various exemplary implementations shown in the figures are merely illustrative representations and are not necessarily drawn to scale.

Perforating tools, e.g., perforating guns or abrasive jet perforating tools, are used in the oil and gas industry for creating perforation cluster in well casings and surrounding formations. Abrasive jet perforating tool includes nozzles that direct a mixture of high-pressure fluid and abrasive particles toward the target area. In operation, the nozzles are often placed in a location in the wellbore facing the target at a fixed standoff distance. Perforating guns can include shaped charges and a perforating gun body. Shaped charges are positioned at specific angles within the gun body and configured to direct high-pressure and high-velocity jets of metal particles toward the well casing and the surrounding rock formation. Abrasive jet perforating tools, with their high fluid flux combined with abrasive particles, offer the advantage of generating perforations of large diameters and free of compaction zones, compared to perforating guns. On the other hand, the perforating guns can create deeper perforations.

The geometry of perforation cluster plays a key role in initiating fractures in the formations at reasonably practical pressures. The geometry of the perforation cluster includes diameter, depth, spacing, azimuth with respect to the borehole/in-situ stresses and/or configuration of perforations. The perforation cluster can have in-plane perforation configuration which includes several perforations in the same plane transverse to the wellbore. The perforation cluster can also have an in-line configuration where all perforations are arranged in the same longitudinal plane but spaced along a straight line on the wellbore surface and oriented towards the same azimuthal direction. Additional configuration of perforation cluster includes a helical configuration, where perforations are phased azimuthally in an increment of 60 degree and arranged in different transverse planes.

This disclosure describes perturbed in-line perforations formed by a bottom hole assembly. In some aspects, the bottom hole assembly includes a downhole conveyance that is extendable from a terranean surface, through a wellbore, and to a subterranean formation. A perforating tool is configured to couple to the downhole conveyance and create a perforation cluster in the subterranean formation. The perforation cluster includes perforations arranged or spaced in-line along a longitudinal direction of the wellbore. The perforations include one or more first perforations extending along a first direction, e.g., a first azimuthal direction. The perforations also include one or more second in-line perforations extending along a second direction, e.g., a second azimuthal direction, at a first offset angle with respective to the first direction, and one or more third perforations extending along a third direction, e.g., a third azimuthal direction, at a second offset angle with respective to the first direction, and so on. In example implementations, the second perforations can be the even-numbered perforations in the perforation cluster, while the third perforations can be the odd-numbered perforations in the perforation cluster and first and second offset angles can be small, such as within ±15 or ±10 degrees range. In this way, the one or more second perforations and the one or more third perforations are alternative with each other along the longitudinal direction of the wellbore. In other words, a second perforation located in the middle of the cluster can be arranged between two third perforations along the longitudinal direction of the wellbore.

Implementations of the present disclosure can provide one or more of the following technical advantages. For example, the techniques described herein can create a perforation cluster with a perturbed in-line configuration. In example implementations, the perforations in a cluster are spaced along the wellbore axis, e.g., the longitudinal direction of the wellbore, and extend radially into the formation at varied azimuthal directions within a small range of angles with respect to the certain principal azimuthal orientation. This perturbed in-line configuration enables the initiation of transverse hydraulic fractures at a lower fracture initiating pressure (FIP) and facilitates further fracture growth under reduced hydraulic pressure. The transverse hydraulic fracture is a preferred orientation in multiple stage fracturing (MSF) stimulation of horizontal well, as the transverse hydraulic fracture can be close to the preferred fracture plane and, when repeated at multitude of wellbore depths, yield larger reservoir contact area. Moreover, utilizing perturbed in-line configurations allows for fracture initiation along the direction of the perforation or in a direction closely aligned with it, thereby offering control over fracture direction by manipulating the perforation orientations. This perturbed in-line configuration can be implemented using various commercially available downhole tools, e.g., perforation guns or abrasive jet perforating tools. In contrast to helical configuration where perforation orientations span a complete circle of 360 degrees, perforations in a perturbed in-line cluster are directed within a narrow azimuthal range with respect to the principal orientation, thus allowing realization of equal standoff distances between individual charges and casing. Equal standoff distances can provide desired consistent perforation diameters, enhancing operational efficiency and wellbore performance.

is a schematic diagram of a wellbore systemthat includes a hydraulically fractured wellborewith a bottom hole assembly. Generally,illustrates a portion of one implementation of the wellbore systemin which wellboreis formed into a naturally fractured subterranean formation (or reservoir)for the production of one or more hydrocarbon fluids to a terranean surface(through the wellboreand, if used, one or more wellbore tubular strings). Fractured subterranean formationthat holds the hydrocarbon fluid(s) can be present beneath several other formation rock layers. The formationcan include a primary porous medium of the formation rock. An irregular system of microscopic fractures and small cavities can be typically present in the primary porous rock medium. Natural fracturesin the formationcan also be present across a wide range of scale, ranging from microfractures to extensive fractures or faults of thousands of meters.

As shown, the wellbore systemaccesses a subterranean formationthat provides access to hydrocarbons located in such subterranean formation. A drilling assembly (not shown) may be used to form the wellboreextending from the terranean surfaceand through one or more geological formations in the Earth. One or more subterranean formations, such as subterranean formation, are located under the terranean surface. As will be explained in more detail below, one or more wellbore casings, such as an intermediate casingand production casing, may be installed in at least a portion of the wellbore. In example implementations, a drilling assembly used to form the wellboremay be deployed on a body of water rather than the terranean surface. For instance, in example implementations, the terranean surfacemay be an ocean, gulf, sea, or any other body of water under which hydrocarbon-bearing formations may be found. In short, reference to the terranean surfaceincludes both land and water surfaces and contemplates forming and developing one or more wellbore systemsfrom either or both locations.

In example implementations of the wellbore system, the wellboremay be cased with one or more casings. As illustrated, the wellboreincludes a conductor casing, which extends from the terranean surfaceshortly into the Earth. A portion of the wellboreenclosed by the conductor casingmay be a large diameter borehole. Additionally, in example implementations, the wellboremay be offset from vertical (for example, an inclined wellbore). Even further, in example implementations, the wellboremay be a stepped wellbore, such that a portion is drilled vertically downward and then curved to a substantially horizontal wellbore portion. Additional substantially vertical and horizontal wellbore portions may be added according to, for example, the type of terranean surface, the depth of one or more target subterranean formations, the depth of one or more productive subterranean formations, or other criteria.

Downhole of the conductor casingcan be the intermediate casing. The intermediate casingmay enclose a slightly smaller borehole and protect the wellborefrom intrusion of, for example, freshwater aquifers located near the terranean surface. The wellboremay than extend vertically downward. This portion of the wellboremay be enclosed by the production casing. Other casings, not specifically shown in this figure, can be included within the wellbore systemwithout departing from the scope of this disclosure.

As shown in, a cement layer(or cement) is installed in an annulus between each illustrated casing (conductor casing, intermediate casing, and production casing) and the adjacent geologic formation (such as subterranean formation). Cementcan be circulated downward, during the construction of the wellbore system, through one or more casings and back upward into the annulus between the particular casing and the adjacent geologic formation in order to, for example, bond the casing to the formation. Once solidified in the annulus, the cementcan provide a barrier to fluid entry into the wellboreas well as maintain the casings in place.

In the schematic of, the wellborehas been hydraulically (or otherwise) perforated to create perforations, each of which, for example, extending through the casing. Multiple perforation clusters,andcan be formed simultaneously or sequentially. Such perforations in the formationcan be accomplished by any known technique (or any technique developed therefore). Although shown as a cased wellbore, the wellbore(for example, at a depth at which the perforation clusters,andare formed) can be an open hole completion (thereby eliminating, in some aspects, the need for perforating through the casing). The perforation clustercan have a common schematic of perforations, as illustrated in. In example implementations, the perforation clustercan have a perturbed in-line perforation configures, as describe with further details in.

A downhole conveyanceis deployed to convey tools and instruments downhole. The downhole conveyanceis extendable from a terranean surface, through a wellbore, and to a subterranean formation. The downhole conveyancecan be a wireline, e.g., a single or multi-strand wire cable. Wireline cables can incorporate conductors for electrical power and data transmission. The downhole conveyancecan be a coiled tubing, e.g., a continuous length of steel or composite tubing wound on a reel which can convey fluids, tools, and equipment into the wellborewhile providing pressure control and flexibility. The downhole conveyancecan also be a slickline, e.g., a single-strand wire or cable used for light-duty operations such as setting or retrieving downhole equipment, taking fluid samples, or conducting basic well interventions. The downhole conveyancecan also be a drilling pipe. Drilling pipes can be used in the drilling process to convey drilling fluids, transmit torque, and carry out other functions necessary for drilling operations.

The uphole end of the downhole conveyancecan be coupled to a top subassembly (not shown). The top subassembly can include various tools and equipment crucial for downhole operations. For example, the top subassembly can include a top drive or a blowout preventer (BOP). The top drive can be a motorized drilling system installed on the drilling rig's mast or derrick. It rotates the drill string, providing the necessary torque and rotational power to drill the well. BOP can be configured to prevent uncontrolled releases of formation fluids (blowouts) during drilling, completion, or production operations. It can include a series of valves and hydraulic mechanisms that can seal off the wellbore, effectively isolating pressure zones and mitigating blowout risks.

In the schematic of, a bottom hole assemblyis shown run into the wellboreon the downhole conveyance(e.g., a wireline, slickline, coiled tubing, or other conveyance). In example implementations, the bottom hole assemblyincludes an abrasive jet perforating tool. The abrasive jet perforating tool utilizes high-pressure abrasive jets to cut through the well and penetrate into the formation. Abrasive jets can be streams of water or another suitable liquid mixed with abrasive materials (e.g., sand or ceramic particles) propelled at high velocity. This method can create larger perforation diameters compared to perforating guns. The abrasive jet perforating tool can have nozzles to direct the abrasive particles toward the target formation. As the abrasive particles propel at high velocities, they effectively cut slots in the well and penetrate the rock, forming perforations.

In example implementations, the bottom hole assemblyincludes a perforating gun. Perforating guns deploy shaped charges that generate high-velocity, concentrated jets of explosive charges. The shaped charges are strategically positioned within the perforating gun, and upon initiation, they create perforations by penetrating the well casings and surrounding rock formations. Perforating guns can achieve greater penetration depths than the abrasive jet perforating tool. They can be valuable in hard or consolidated formations where the focused energy from the shaped charges allows for efficient perforation. The choice between an abrasive jet perforating tool and a perforating gun depends on several factors, including formation characteristics, wellbore conditions, and geometry required for perforations.

The geometry of perforations can play an important role in well productivity, reservoir management, and overall operational success. For example, the size and diameter of perforations directly impact the flow of fluids between the reservoir and the wellbore, and pressure distribution during hydraulic fracturing. Larger perforations allow for increased flow rates and faster hydraulic fracture initiation and propagation. The spacing between adjacent perforations determines the density of the induced fractures. In addition, perforations serve as the initial points of contact between the wellbore and the formation during hydraulic fracturing. The depth of the perforations influences the direction and extent of fracture propagation. Further, the orientation of perforations relative to natural fracture networks or bedding planes can influence well performance. In some cases, aligning perforations perpendicular to natural fractures or bedding planes can enhance reservoir connectivity and productivity. In general, consistent perforation geometry, e.g., diameter, depth, and/or space, helps prevent flow imbalances and production inefficiencies.

As shown in, a control systemcan be communicably coupled (wired or wirelessly) to the bottom hole assemblyto operate the bottom hole assembly. The control systemcan include a computer-readable medium (e.g., a non-transitory computer-readable medium) storing computer instructions executable by one or more processors. The one or more processors can execute the stored computer instructions to perform operations described in this disclosure. The control systemcan be configured to control the fluid pressure. This includes monitoring, adjusting, and maintaining the pressure of the fluid circulating during well operations. Additionally, the control systemcan be configured to respond to various inputs or triggers, automatically adjusting the fluid pressure as necessary to accommodate changes in operating conditions or demands. Furthermore, the control systemcan control operations of the bottom hole assembly. For example, the control systemcan control the timing of the perforating shots, adjust the position (e.g., target depth) and orientation of the perforating tool, and/or initiate explosive charges.

Although not shown in, it is understood that the wellborecan include a horizontal portion, e.g., a horizontal well parallel to the terranean surface. In general, a horizontal well is drilled horizontally through a reservoir formation. The horizontal well can intersect more reservoir rock compared to a vertical well. This allows for increased contact with the hydrocarbon-bearing formation, which can enhance production rates of oil or gas.

thoughC illustrate schematic views of example perturbed in-line perforations to induce transverse fractures. More specifically,illustrate three-dimensional (3D) views of the example perforations, andillustrates a view of the example perforations as they are projected in a traverse plane. As shown, the perforations are arranged along a direction, e.g., Z direction in. In example implementations, the perforations include one or more first perforations, one or more second perforationsand one or more third perforations. The perforations,,can be implemented as perforationsin.