TECHNICAL FIELD

This disclosure relates to apparatus, systems, and methods of collecting core samples, and more particularly to collecting sidewall cores while drilling.

BACKGROUND

Core data is often used as a reference for other wellbore measurements, such as for interpreting logs and well tests for lithology, porosity, permeability, wettability, fluid content, as well as fluid properties such as viscosity, density, and compressibility. As such, collecting formation core samples is a crucial part of oil and gas exploration and development. Conventional coring is typically performed by replacing a drilling bit with a coring bit when the top of a targeted zone to be cored is reached. However, this process requires pulling the drillstring out of wellbore multiple times to perform bit replacement and to perform multiple coring runs in order to capture multiple cores with a particular limited core length (such as 30 feet long).

Alternatively wireline sidewall coring tools can be used to obtain sidewall core samples at targeted intervals. However, sidewall coring using wireline tools also requires that the drilling assembly be removed from the wellbore in order to run the wireline coring tool into the wellbore, which can be time-consuming and, therefore, costly, especially in high angle and horizontal wells where wireline needs to be replaced by coil tubing or drill pipe for conveying sidewall coring tools.

In addition, in situations where borehole stability is an issue, such as wellbores containing washouts, conventional coring and wireline sidewall coring tools cannot be used to effectively capture core samples. It is also very difficult and costly to conduct conventional coring or wireline side-wall coring in highly deviated wells or horizontal wells, especially in very long total depth wells located in challenging environments such as deep water wells, for which making a trip in and out of the well can be a time consuming cost prohibitive operation.

SUMMARY

In an example implementation, a system includes a bottom hole assembly and a core sampling tool. The bottom hole assembly includes a housing and a drill bit coupled to the housing. The core sampling tool includes a first compartment positioned within the housing, the first compartment including a motor; a second compartment positioned within the housing and radially spaced apart from the first compartment, the second compartment including a coring bit; and a flexible drilling shaft extending between and coupled to the motor and the coring bit.

This, and other implementations, can include one or more of the following features. The first compartment and the second compartment can be vertically spaced apart within the housing of the bottom hole assembly. The first compartment can include a first actuator configured to raise and lower the motor within the first compartment. The second compartment can include an opening through the housing; and a sealing door configured to seal the opening; and lowering the motor within the first compartment can cause the coring bit to extend outside the second compartment through the opening when the sealing door is positioned above the opening. The second compartment can include a second actuator configured to raise and lower the sealing door within the second compartment; and positioning the sealing door above the opening can include causing the second actuator to retract a connecting rod coupled to the sealing door. The sealing door can be configured to seal the opening during drilling operations. The second compartment can include a core storage container. The coring bit can be configured to rotate to deposit a core sample within the core storage container. The coring bit can coupled to the flexible drilling shaft using one or more locking joint pins; and the second compartment can include a locking joint pin releaser configured to unlock the one or more locking joint pins coupled to the coring bit. The second compartment can include a rotatable actuator configured to rotate the coring bit within the second compartment. Rotating the coring bit to deposit core samples within the core storage container can include inserting the one or more locking joint pins into the locking joint pin releaser to unlock the one or more locking joint pins; and actuating the rotatable actuator to rotate the coring bit within the second compartment. The second compartment can include a second connecting rod coupled to the rotatable actuator; and a rotatable bit housing coupled to the rotatable actuator, the rotatable bit housing encircling the coring bit when the coring bit is positioned with the second compartment; and actuating the rotatable actuator to rotate the coring bit within the second compartment can include causing the actuator to extend the second connecting rod. The second compartment can include a third actuator; and a core disposing pin coupled to the third actuator. Depositing the core sample within the core storage container can include rotating the coring bit from a neutral position to a depositing position over the core storage container; and extending the core disposing pin using the third actuator through the coring bit. The second compartment can include a fourth actuator; and a plug coupled the fourth actuator and configured to seal the core storage container. Sealing the core storage container can include determining that the core storage container is full; in response to determining that the core storage container is full, actuating the fourth actuator to position the plug over the core storage container; and inserting the plug into the core storage container. Inserting the plug into the core storage container can include extending the core disposing pin using the third actuator to press the plug into the core storage container. The system can include an anchor shoe configured to stabilize the bottom hole assembly within a wellbore; and a third compartment within the housing, the third compartment including a fifth actuator; a first leg rotatably coupled to the anchor shoe and the fifth actuator; and a second leg rotatably coupled to the anchor shoe and the third compartment. The third compartment can be vertically spaced apart from the first compartment and the second compartment and radially spaced apart from the second compartment within the housing.

In some implementations, a core sampling tool includes a first compartment positioned within a housing, the first compartment including a motor; a second compartment positioned within the housing and radially spaced apart from the first compartment, the second compartment including a coring bit; and a flexible drilling shaft extending between and coupled to the motor and the coring bit. The coring bit is configured to cut core samples from a targeted formation.

Example embodiments of the present disclosure may include one, some, or all of the following features. For example, a core sampling tool according to the present disclosure may be used during drilling operations without requiring removal of the drilling tool from the wellbore. As a result, a core sampling tool according to the present disclosure may reduce the time and cost required to collect core samples by allowing for core sampling during drilling operations. In addition, a core sampling tool according to present disclosure may minimize flow restrictions along the drill pipe as a result of the radially offset chambers of the core sampling tool. A core sampling tool according to the present disclosure may also allow for sampling in deeper portions of a formation compared to sampling with traditional sampling tools. A core sampling tool according to the present disclosure may enable core sampling in highly deviated wells and/or horizontal wells. In addition, a core sampling tool according the present disclosure may allow for core sampling in boreholes with stability problems, such as wellbores with borehole washouts.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

