Kaiser acoustic emission ground stress testing study on shale oil reservoir in Y block of Ordos basin, China.

Abstract

The determination of rock mechanics parameters and in-situ stress during the development process of "horizontal well + volume fracturing" for shale oil reservoirs in Block Y of the Ordos Basin can provide a basis for fracturing schemes and production pressure difference design. Rock mechanics experiments are the most direct method for determining rock mechanics parameters. This article tested the in-situ stress of the Chang 7 shale oil reservoir in Block Y of the Ordos Basin through Kaiser acoustic emission experiments, calculated the static rock mechanics parameters of the block, and found that the vertical principal stress distribution of the Chang 7 section of the block is between 49.72 ~ 61.13 MPa, the maximum horizontal principal stress distribution is between 59.04 ~ 75.4 MPa, the minimum horizontal principal stress distribution is between 46.75 ~ 56.38 MPa, the horizontal stress difference is between 10.16 ~ 21.67 MPa, and the horizontal stress difference coefficient is between 0.21 ~ 0.42. The average maximum horizontal stress gradient is 2.534 MPa/100m, the average minimum horizontal stress gradient is 1.891 MPa/100m, and the average vertical stress gradient is 2.051 MPa/100m. In addition, dynamic rock mechanics parameters can be calculated using well logging curves, and a relationship model between dynamic and static rock mechanics can be established. Through calculation, the error can be obtained within 16%, which meets practical engineering requirements and can be applied in mining practice. The core experimental data is limited, discrete, and unable to reflect the trend of rock strength changes throughout the entire well section. By using logging curve data to predict rock strength parameters, continuous formation strength profiles can be obtained, providing important basis for later layer selection, section selection, and prediction of fracture direction.