The Mechanical Properties of Three Types of Shale Oil Reservoirs and Its Influence on Hydraulic Fracturing

Abstract

ABSTRACT: The premise of hydraulic fracturing is to have an accurate and detailed understanding of the rock mechanical properties and fracture propagation law of shale reservoir. In this paper, a systematic and comprehensive evaluation of the mechanical properties is carried out based on the shale oil reservoir in the south of Songliao Basin, Jilin Province. Based on the analysis of the mineral composition, the microstructure, rock mechanics of three types of shale oil reservoirs in the laboratory, combined with the field fracturing, logging data and the in-situ stress, the fracture propagation law of the three types of reservoirs is obtained, and the suggestions for fracturing are put forward. The results showed that there are two significant characteristics in the study area. One is the development of bedding, which is easy to form horizontal fractures. Influenced by bedding and stress, it is not suitable for horizontal well fracturing. The other is the high content of clay minerals, and the applicability of conventional slick hydraulic fracturing fluid is poor. It is suggested to use vertical well or directional well to carry out volume fracturing. In this way, the effect of bedding can be effectively used to open and communicate the bedding and form a larger fracture network. 1. INTRODUCTION Hydraulic fracturing is the key technology of shale oil and gas development. Through large-scale volume fracturing of shale oil and gas reservoir, a dispersion volume fracture network (volume fracturing) is formed (Cipolla et al., 2008), so that shale oil and gas stored in ultra-low permeable shale reservoir can be developed industrially (Cipolla et al., 2008; Guo et al., 2014; Sierra et al., 2010). The premise of hydraulic fracturing is to have an accurate and detailed understanding of the rock mechanical properties and their influences on hydraulic fracture (Vernik et al., 1992; Vernik et al., 1997; Clarkson et al.,2013). The formation and extension mechanism of hydraulic fracture in shale oil reservoir is complex. It is of great significance to master the formation mechanism of artificial fracture network for evaluating the effectiveness of hydraulic fracturing.