Anisotropic Detection Analysis and Pilot-Well-Integration Inversion for Array Resistivity Logging in a Horizontal Well

Summary Horizontal well drilling technology, which increases the contact area between the target layer and the borehole, is widely used in the development of unconventional tight oil/gas reservoirs, significantly improving the rate of oil and gas recovery. A direct current (DC) logging instrument (e.g., an array-laterolog-type instrument) is usually used to evaluate the resistivity of fluids and rock in the reservoir. However, the responses of array laterolog are mainly affected by surrounding formations, layer interfaces, and anisotropy in horizontal wells, posing challenges for fine reservoir evaluation. To investigate the detection performance of the array laterolog instrument, the boundary detection factor is defined in this paper using 3D finite element forward modeling. The responses of array laterolog in anisotropic formation with horizontal well are fully investigated as well as the qualitative and quantitative assessments. The adaptive modified Levenberg-Marquardt (AMLM) inversion algorithm is used to derive the 2D resistivity profile from the array laterolog measurements. The pilot-well-integration inversion method is proposed to reduce the number of inversion parameters and ensure the quality of inversion results. Moreover, the domain decomposition scheme is designed to accelerate the inversion process. Synthetic and field data are processed to illustrate the detailed implementations as well as the performance of the proposed method.