New Multilayer Boundary-Detection Service in Bohai Bay, Northern China

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 176442, “New Multilayer Boundary-Detection Service Employed in Complex and Mature Reservoir in Bohai Bay, Northern China,” by Xija Guo, Yong Jia, Kai Fan, Liuhe Yang, and Guoquan Zhao, CNOOC, and Kai Wu, Fei Wang, Cang Li, and Zhujun Gao, Schlumberger, prepared for the 2015 SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition, Nusa Dua, Indonesia, 20–22 October. The paper has not been peer reviewed. Bohai Bay is northern China’s largest offshore basin. Its predominant depositional environment is a shallow delta and a meandering river system complicated by faults, an arrangement that leads to fully developed interbed interference and high geological uncertainty when horizontal wells are drilled within the greenfield. As a solution to resulting challenges, a new multilayer boundary-detection service has been introduced. This paper illustrates a case study in which this technology was applied. Introduction In 1967, CNOOC began commercially operating the oil and gas resources of the Bohai Sea (Fig. 1). Since then, more than 100 production platforms have been put into operation in a 43 000-km2 exploration area, including both development projects on the greenfield and infill projects on the brownfield. After long-term development and production, an increasing number of conventional reservoirs have a depleted hydrocarbon capacity and the field’s water cut has increased quickly. Thus, the CNOOC client began to focus on the complex marginal reservoir and the infill projects of the brownfield. The focus of this paper is to help achieve the geological objectives and, furthermore, optimize production by use of the new multilayer boundary-detection service. Background General Geology. The Bohai Bay basin formed at the end of the Tertiary on a crystalline basement solidified from the Archeozoic to the Early-Middle Proterozoic. After deposition in the Middle to Late Proterozoic and the Paleozoic, Mesozoic, and Cenozoic, a complex fluvial channel system was generated with features such as disconnected and isolated sand bodies, mingled structures between the hydrocarbon reservoir and aquifer, inconsistent properties both vertically and laterally, and fully developed heterogeneity. As of 1994, the Bohai Bay basin has been known to consist of 47 faulted depressions, in which 170 oil and gas fields have been found.