Comprehensive Analysis the Casing Deformation in Shale Gas Reservoir Modification by Seismic and Microseismic Technology

Abstract

In recent years, Chinese shale gas exploration and development has made significant process, the multi segment mass volume reform of hydraulic fracturing has accelerated the pace of shale gas exploration in China. Although profit of oil and gas field development enhanced, the casing is influenced by the heterogeneity of cement sheath, formation and pore pressure, which led to casing deformation. It restrict severely safe and fast production shale gas wells. This paper studied the stratum stress change and comprehensive analysis the reason of casing deformation by microseismic monitoring data, and analyzed the relationship between reservoir heterogeneity by seismic attribute data to, natural fracture development and casing deformation, this is to optimize the fracturing design, adjust the scale of the fracturing, and reduce the risk of casing deformation. There are many factors influencing casing deformation, they are mainly divided into geological and engineering. The direct cause is that stress changes around casing, and the stress over bearing range, which lead to deformation. In the process of hydraulic fracturing, the micro seismic events are very active around the well trajectory or below well trajectory in the position of casing deformation. Then the subsequent fracturing micro cracks are communication, until the fracturing section produces a lot of events, now the sharp change of formation stress can lead to casing deformation. The seismic attributes information are main consist of fracture property and elastic parameter inversion. Using different attributes according to the different geological structure of the reservoir, for example, it used curvature in the area of the destination layer, coherence emphasis can be used in the regions with strong anisotropy; The elastic parameter inversion profile can be used to invert the anisotropy of reservoir. The parameters of the large reservoir lithology is different in the interface of S-wave impedance inversion section, it is easy to casing deformation. The paper used two aspects of seismic attributes and microseismic monitoring to analysis the characteristics and causes of casing deformation, and put forward relevant technical improving scheme. It improved efficiency and reform effect of southwest oil and gas reservoir, and further advanced the shale gas reservoir reform technology.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017