Multi-Interbedded Continental Shale Reservoir Evaluation and Fracturing Practice

ABSTRACT: Continental shale oil resources are abundant in Sichuan Basin in China, according to multiple limestone interbeds and variable longitudinal stress characteristic, continental shale reservoir characteristic evaluation method including radar map, geological sweetness and fracability index, were established considering multi-thin interlayer, horizontal stress difference, etc. The continental shale in area A demonstrates the characteristics of high clay mineral content with strong plasticity and serious heterogeneous. The fracture geometry inverse analysis is established based on the results of microseismic monitoring and numerical simulation, the continental shale has simple fracture geometry and lower fracture length propagation rate. Further reducing cluster spacing and increasing fluid intensity are the technological directions to improve the SRV of fractured wells in area A. The study could provide guidance for the shale evaluation and fracturing program design of continental shale oil wells. 1. GEOLOGICAL CHARACTERISTICS OF CONTINENTAL SHALE There are abundant shale oil and gas resources in the Sichuan Basin in China. At present, the marine shale gas have developed commercially especially in Wufeng & Longmaxi formation, and the continental shale oil resources are important strategic replacement resources (Wei et al, 2022; Shu et al, 2023; Guo et al, 2023; Jin et al, 2023; Zhao et al, 2023; Yu et al, 2023; Wang et al, 2023). Compared with the marine shale oil and gas reservoirs, continental shale in area A is of strong heterogeneity and low oil & gas abundance, the formation is strong plastic with clay mineral content more than 50%, and multiple limestone interbeds exist resulted in variable longitudinal stress, the higher shale thermal evolution leads to complex fluid properties and aggravates the difficulty of multiphase flow (Jiang et al., 2023; Shu et al, 2023; Sun et al, 2023; Wang et al, 2023). Because the huge geological charactristic between marine shale and continental shale, bottleneck problems such as fracture height and fracture complexity limit emerge in conventional hydraulic fracturing technology, which greatly restricts the effective exploration and economic development of continental shale oil & gas (Jiang et al, 2023). Thus, the reservoir characteristic and fracturing effect evaluation method should be developed according to the field cases. 2. COMPREHENSIVE EVALUATION OF RESERVOIR PARAMETERS 2.1. Radar map of key geological parameters Key geological parameters such as clay minerals, interlayer thickness, natural fracture, etc., and rock mechanics parameters such as horizontal stress difference and Poisson's ratio, etc., were selected as evaluation data set to draw a non-dimensional rose map of the above 9 parameters to qualitatively show the differences in geological parameters among wells.