RIASSUNTO
Abstract
Shell China, in partnership with PetroChina Southwest, began exploration of the Fushun Shale Gas Block, completing its first wells in 2011. A campaign was designed to acquire subsurface data in the exploration campaign to assess the Lower
Longmaxi Hot Shale interval with an end goal of assessing the feasibility of a shale gas field development in the block. As part of the first phase of the exploration campaign, two vertical wells were drilled and completed followed by three horizontal
wells.
Over the execution of the first two vertical wells significant performance improvement was achieved by the service contractors involved in the project, resulting in decreased Non Productive Time (NPT). Significant preparation was conducted in order to prepare both local and international contractors for the horizontal wells in the campaign. In order to deliver the horizontal completions in an efficient manner, the Fushun team implemented learnings gained through similar projects in North America. Preparation for the horizontal well campaign included arrangement of the source water with the local community, ordering new equipment capable of completing the work, cross-posting of service contractors to unconventional assets in the U.S., and movement of experienced site-supervisors to support the Fushun project. The fracture design was also improved on each well in the campaign delivering more proppant per stage, key towards optimizing hydraulic fracturing and maximizing production potential.
Through the initial phase of exploration activities, a shale gas play in the Fushun Block has been confirmed. Operational challenges and technical learnings that were experienced in the initial exploration wells will be carried into the next phase of
appraisal.
Introduction
In November 2009, PetroChina and Shell China entered into an agreement to jointly explore for shale gas in the Sichuan Basin of China. The study block straddles the border between the Sichuan Province and Chongqing Municipality. The location of the block can be seen in Figure 1.
The main objective of the exploration activity is the lower Silurian interval referred to as the Lower Longmaxi Hot Shale. The focus on the Silurian is based on the presence of gas shows detected in this zone on previously drilled PetroChina wells. A section of the Sichuan Basin stratigraphic column showing the Silurian interval is shown in Figure 2.
The systematic process for evaluating shale gas fields has been previously documented1 and began as a study of data from previously drilled wells, outcrops and literature reviews. As of April 2012, five deep exploration wells have been drilled
across the study area to acquire data necessary to assess the Longmaxi interval's shale properties, hydrocarbon properties and producibility. Data acquisition plans and well designs were worked on by the project team to support the execution of the exploration well campaign. Significant learnings and best practices were brought from North America for these activities.