BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

Generally, this disclosure relates to a tri-axial centrifuge apparatus for testing of petro-physical properties and gathering of geo-mechanical information.

Description of the Related Art

There are a number of limitations related to methods, techniques, and instruments utilized for reservoir sample testing and analysis. The most basic step in any reservoir study is sample preparation. Improper or ineffective cleaning practice to bring a sample to a native (original) state can render all efforts of testing and analyses in vain. This step is the most detrimental to sample analysis, especially in tight unconventional formations, gas shales, and conventional formations of dual porosities. The various current cleaning process have limitations of achieving proper capillary pressure to effectively remove impurities from test samples in order to prepare them for tests and analysis. Attempts to overcome these issues by utilizing harsh processes of heated solvents or high flow methods are ineffective. In many instances, such practices alter the wettability of test sample, thus defeating the primary purpose of cleaning the test sample. These artificial alterations in wettability and fluid saturations caused by various known sample restoration techniques create significant errors in petro-physical data collected for reservoir evaluation. In unconventional (gas shale) reservoir analysis, the conventional cleaning procedures are also largely ineffective because they do not take into account the capillary effect. When the reservoir is formed, hydrocarbons migrate into reservoir rock replacing water that was initially present. This is a capillary driven mechanism and there is a need to recreate this scenario in laboratory studies to mimic the reservoir process.

Once a sample is restored, it can then be subjected to various petro-physical tests and analyses. Currently, there are a series of tests performed on different instruments to obtain various petro-physical data needed for reservoir characterization and production analysis. Typically, several instruments are used to perform electrical properties analysis to calibrate the electrical log, fluid saturation analysis, and analysis of Archie's parameters. Another apparatus is needed to perform capillary pressure above 1000 psi analysis, one to perform fluid wettability analysis, one to perform acoustic velocity for dynamic mechanical properties, and yet another apparatus to perform x-ray for saturation distribution. Currently, there is no instrument that can perform many of these tests under tri-axial conditions that are observed in the field.

The need of such an apparatus is immense, especially for evaluation of unconventional sources, such as tight gas sand, shale, tar sand, and hydrates, as the conventional apparatus in the industry do not perform adequate analysis of these formations.

Additionally, existing centrifuge methods are flawed. The sample holders used in existing centrifuges cannot apply tri-axial stress on the sample, as such samples typically fail at RPM higher than 10,000. The capillary pressure such centrifuge devices can attain is not sufficiently high enough to duplicate conditions found in some reservoirs, especially unconventional and depleted reservoirs. With many of the current centrifuge methods, the measurement for saturation is based on fluid differentiation and does not incorporate the actual distribution of fluid in a test sample. Additionally, the test chambers typically used to hold the test sample cannot handle most of the corrosive chemicals that are required during the life cycle of sample tests (e.g., solvents, inhibitors, surfactant, enhanced oil recovery (EOR) chemicals and acids). Another concern with current centrifuge methods is that the necessary measurements of rock electrical properties are not collected continuously throughout the test. Additionally, the orientation of the test specimen and its distance from the center of the centrifuge axis, has been problematic with current centrifuge methods.

In every stage of reservoir exploitation, accurate information about fluid saturation, pore distribution, capillary pressure, and permeability is vital. In the exploration stage, such information provides estimates for original hydrocarbon in-place and maximum primary production. In later stages of reservoir life cycle, it helps determine various secondary and tertiary enhanced oil recovery options, particularly for a most cost effective and profitable scenario. During abandonment of the well, the saturation values are imperative to assist in the design of a proper abandonment, such as complete shut off or maintenance for possible future intervention.

SUMMARY OF THE DISCLOSURE

A tri-axial centrifuge apparatus for testing of petro-physical properties of a test sample and gathering of geo-mechanical information includes a tri-axial sample holder located within an inner bore of a cell body. An axial pressure fluid supply line is operable to deliver an axial pressure fluid to a fluid chamber of a piston assembly to apply an axial pressure on the test sample. A confining pressure fluid supply line is operable to deliver a confining pressure fluid to a cell chamber of the cell body to apply a biaxial confining pressure on the test sample. A test fluid holder contains test fluid. The test fluid holder is sealingly secured to the cell body and static relative to the cell body. The axial pressure fluid, the confining pressure fluid, and the test fluid are contained in separate flow systems. A centrifuge has a window that is located on a portion of a path of the tri-axial sample holder. The tri-axial sample holder is loaded in the centrifuge and spinning with the centrifuge. An x-ray instrument is static and is aligned with the window of the centrifuge.

In alternate embodiments the tri-axial centrifuge apparatus can further include a titanium tri-axial test casing, and the tri-axial sample holder can be located in the tri-axial test casing. The test fluid holder can include glass. The centrifuge can have an at least one additional tri-axial sample holder. The centrifuge can include at least two glass windows. The at least one electrical sensor can be operable to gather data during the testing of a sample and store data for downloading at a later time. The at least one acoustic sensor can include a transducer. The x-ray instrument can be operable to perform an x-ray scan while the centrifuge is operating. The apparatus can further include a fluid camera system. The test fluid holder can have an electrical measurement feed.

In other alternate embodiments, the tri-axial centrifuge apparatus can further include an electrical measurement jacket. A piston seal can form a seal between an inner bore of electrical measurement jacket and an outer diameter of a piston member of the assembly. A base seal can form a seal between the inner bore of the electrical measurement jacket and a base member of the tri-axial sample holder. The piston seal and the base seal can seal the test fluid from the cell body outside of the electrical measurement jacket.

In yet other alternate embodiments, the tri-axial centrifuge apparatus can include a tri-axial test casing. The at least one acoustic sensor can be rotationally fixed relative to the tri-axial test casing. A test fluid circulation system can have a test fluid line extending between the tri-axial sample holder and the test fluid holder and a fluid circulation line extending outside of the cell body between the test fluid holder and the tri-axial sample holder. The test fluid circulation system can provide a fluid circulation path for the test fluid. The piston assembly can be an axially oriented piston assembly with a piston stem located entirely within the inner bore of the cell body. The axially oriented piston assembly can be operable to apply the axial pressure on the test sample that is greater than the biaxial confining pressure applied on the test sample, and be operable to apply the axial pressure on the test sample independent of increasing the biaxial confining pressure on the test sample.

