The study and application of the subtle strike-slip fault identification technology in the exploration of Miaoxinan uplift area , Bohai Bay Basin, Eastern China

Abstract

The Miaoxinan uplift located in the eastern of Bohai Bay Basin, was an important exploration area. The Penglai 19-3 oilfield, found in its western Bonan low uplift, is China's largest offshore oilfield, the Penglai 9-1 oilfield, found in its northern part of Miaoxibei uplift, is the largest oilfield discovered for the past few years in Bohai oilfield. However, in Miaoxinan uplift area, the fracture system is very developed and the structure is very broken because of the development of the North-south Tancheng-Lujiang strike-slip fault, the Near-east Zhangjiakou-Penglai fault and the North-east Extensional fault. By means of geophysical properties, forward modeling, combined with field outcrop and sandbox physical simulation, this work establishes the technological process of identifying the subtle strike- slip fault by fault likelihood attribute based on the construction oriented filtering.Using this technique, a subtle strike-slip fault was identified in the low part of Penglai 20-A structure, and the Penglai 20-B structure was found.The PL20-B-1 well drilled in 2015, the total oil reservoir thickness of the well is 51 meters, confirmed the reliability of this subtle strike-slip, but also proved the feasibility of the technology.In the subsequent drilled of the 5 wells, there were about 35 meters of oil layer for each well found. However, there was a contradiction with the high-site PL20-B-2 well and the low-site PL20-B-5. Most of the PL20-B-5 well were oil layers in Guantao formation, while most of the PL20-B-2 well were oil and water layers in the same formation. Using the above technology, a subtle strike-slip fault extending about 1km was found, which solved the contradiction between two wells. The subsequent deployment of PL20-B-6 well found 60 meters of oil reservoir, upgraded 6.48 million tons of proven oil reserves.In the evaluation process of Penglai 13-A structure in the northern part of the study area, a new subtle strike-slip fault was identified by using the above method, and the 1.3km² of the trap area was increased, which lays the foundation for the well position deployment in Penglai 13-A structure. With the depth of exploration, the larger structural traps are less, but the use of subtle strike- slip fault identification technology can find new structural traps in the development area of the strike- slip fault, which will help the exploration decision. This method has achieved good application effect in the development zones of strike-slip fault in Bohai oilfield, and can be extended to other oilfields with strike-slip fault development.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019