China's Marine Qiongzhusi Shale Play: First Deep Asia Pacific Region Horizontal Multiple Stage Frac: Case History, Operation & Execution

Abstract

During the past five years, shale gas developments have changed the game for the US natural gas industry. Globally, shale exploration activities are also increasing. China is in the early stages of exploiting the world's largest reserves of shale gas resources while attempting to cope with increasing energy demands.This paper presents a case history of applicable technology currently used in North America for initial attempts at shale gas exploration in China. This case study is the first Cambrian age marine shale well in the Qiongzhusi formation located in the shale-gas-rich Sichuan province.Many technologies were brought from North American shale gas applications for this well (Chong et al. 2010). This study describes the technologies used to drill and complete the targeted shale gas formation and guide the completion and stimulation design. The target formation was drilled horizontally and the casing was cemented. The formation was then stimulated with multiple stages after full integration of data from geologic, geomechanical, petrophysical, and core analysis, which aided in the fluid and proppant selection, proppant concentration, and the designed injection rate. A diagnostic fracture injection test (DFIT) was performed before the main treatment to confirm fracture gradient, closure, pore pressure, system permeability, and leakoff. Microseismic mapping was also used, which proved to be valuable when planning and assessing the fracturing results.Currently, the well is flowing gas at rates comparable to early production time in a typical North American shale gas well with a similar type of completion.This case study serves as an example of successful implementation of proven technology outside of the North America shale gas market. Continued projects such as this one are the predecessor to full-scale development of shale gas and have helped shape the abundant gas supply currently in the United States. Additionally, these types of projects are necessary to help China improve their future outlook on gas supply.

New Analytical Method to Evaluate Casing Integrity during Hydraulic Fracturing of Shale Gas Wells

“…e stress matrix in the wellbore coordinate system is σ. According to the right-hand rule, the direction cosine matrices rotating around X-axis, Y-axis, and Z-axis are shown in equation (1) [21]. e wellbore boundary stress is obtained by the three-dimensional rotations from the principal in situ stress coordinate system shown in equation 3: Before loading where C xα x , C yα y , and C zα z are the coordinate rotation matrices of the x, y, and z directions; σ 0 and σ are the stress matrices in the principal stress coordinate and local wellbore coordinate systems; and α x , α y , and α z are the rotation angles in a counterclockwise direction when looking towards the origin coordinate.…”

“…e complex downhole environments-high pressure and large temperature variation-increase the risk of casing deformation. e volume fracturing technique effectively reconstructs shale reservoirs; however, frequent and serious casing deformation failures occur [1]. ere were over 36 wells with casing deformation (including 112 horizontal wells by 2017) during fracturing process in some shale gas plays.…”

Analytical Method to Evaluate Casing Stress during Multi-Fracturing for Shale Gas Wells

“…The complex downhole environments-high pressure and large temperature variation-increased the risk of casing deformation. The volume fracturing technique effectively reconstructs shale reservoirs; however, frequent and serious casing deformation failures occur [1]. There were over 36 wells with casing deformation (including 112 horizontal wells by 2017) during fracturing process in the some shale gas plays.…”