Technology Feasibility and Production Driver Study in the First Integrated Shale Gas Block in Sichuan Basin
Authors: Liang Xing , Jiao Yajun , Wang Gaocheng , Zhang Lei , Chen Zhipeng , Zhou Xin , Luo Yin , Wang Yue , Han Shim Yen , Zhang Rui , Wen Cheng 
Published: November 2015

As the pioneer of shale gas exploration in China, Longmaxi formation that located in the lower Silurian system in Sichuan basin has entered the developing phase. Under the geological background, seismic and multi-exploration wells’ data analysis, it has been proven that the shale gas play in Longmaxi is more complex than it's equivalents in North America. Though the deeper burying depth of Longmaxi has bring extra bonus by higher pore pressure (1.7 to 2.0), Longmaxi is lagging back in some key reservoir quality indicators such as kerogen content and porosity, same time, the compressional tectonic setting and relative active plate movement develop faults and fractures in an unpredictable way brings extra challenge. Driven by the complexity, more and more technologies have been deployed in the development phase to better define the play. Among them, well placement with real-time image, LWD or wireline logging for reservoir quality (RQ) and completion quality (CQ) evaluation and engineering optimized completion design have been recognized as critical steps in better understand shale gas production based on abroad experience. Although it's always appealing to run the integrated methodology with multi-source data for each horizontal well, the tight economic return is preventing field wide implementation.

This paper studies multi-well data from an integrated project with PetroChina ZheJiang in Zhao Tong block; examines data acquired from 3 laterals drilled in the same direction in the same pad but utilized different combination of technologies including well placement with real-time image, LWD quad-combo logging with spectroscopy and engineering optimized fracture design. By investigating the micro seismic data and production rate from each lateral, correlation were made to identify the key production drivers and finally lead to the conclusion of the most economic and efficiency technology combination for the horizontal wells development pattern in Sichuan Basin.

In conclusion, laterally the heterogeneity of reservoir quality for the same layer in the target platform is not the key production driver. However, reservoir quality and three principal stresses along vertical scope, combining with the nature fracture distribution make a big difference for the completion fracture extension and production rate. As a result, well placement with bedding identification ability being a prevention methodology is quite critical in the mountainous area in Sichuan basin. LWD logging and an engineering optimal completion design based on that provide comprehensive understanding for each lateral should be deployed based on several considerations including well trajectory, heterogeneity, etc.

In the early stage of shale gas development of China, utilize the very first block with integrated service to grab the full value of seamless technology and move forward to solve the conflict between the exploration needs and economic return will shed some lights on the development direction in Longmaxi layer.