A Geomechanical Study and Hydraulic Fracture Geometry Analysis of the Longmaxi Shale in South China
Jin, Yan; Li, Qinghui; Chen, Mian
The Longmaxi Shale formation exposed in South China is a Silurian black shale sequence and a reservoir that has high shale gas content and medium to high maturity, which is now producing with the aid of stimulation by hydraulic fracturing. Laminated bedding plane are the main factors causing the mechanical anisotropy of the formation. Locally, the bedding plane is continuous and pinched out unpredictably. Laminated bedding plane, coincide with other natural fractures, affects the hydraulic fracture geometry and the stimulated reservoir volume notably and needs to be studied in depth.
Samples collected from representative exploratory wells and outcrops are being targeted to establish a geomechanical and diagenetic framework for the reservoir. Compressive and tensile strength testing and potential active fracture analysis of core plugs from each sample and example well are used to characterize fracture development and enhancement of permeability in the target zones. Ductile to brittle change of samples are studied by conducting correlative tests under simulated environment, which gives us a real view of the rock behavior in reservoir situation. Thin section petrography helps constrain aspects of the diagenetic recording natural porosity, permeability, and replacement of carbonate by silica and calcite. Laboratory scale hydraulic fracturing experiments are taken and CT-scanning techniques are used to analysis hydraulic fracture propagating behavior in black shale blocks which are getting from representative outcrops.
This work will illustrate the ductile-brittle geomechanical properties of shale formation and will describe the record of diagenesis at producing intervals. Results from geomechanical testing and laboratory hydraulic fracturing will help determine the optimal directions for horizontal drilling and hydraulic fracturing in the Silurian unconventional reservoir.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013