High-Resolution VSP Imaging To Locate Additional Reserves in Producing Fields

Abstract

Abstract In southern Louisiana many of the mature oil and gas fields are piercement salt domes where geologic structure often results in fragmented, although prolific, reservoirs throughout the fields. Surface seismic and geological data have proven reliable for exploration drilling in these reservoirs. This information, however, is not adequate to define the small fragmented reservoirs encountered in development drilling. The use of borehole seismic imaging to define structure in exploration wells is a common practice. However, these surveys have typically lacked the accuracy to be used reliably in a development environment. Traditional borehole seismic surveys were adjusted to run inside tubing and inside casing while enhancing the resolution required to make development drilling decisions. By defining the reservoir extent, an operator can confirm economics before additional development drilling. A case study examines the specific seismic imaging technologies used to define the updip limit of a reservoir from an existing production well. A three-component, multi-receiver tool and marine vibroseis source technology were applied with advanced wave field processing to provide the resolution required to meet the objective of defining reservoir extent. Lake Fausse Pointe Imaging Project Introduction A majority of the oil and gas fields in southern Louisiana have been producing for over 40 years, therefore, area operators are seeking new technologies to expand their producible reserves. Because many of the fields are the result of piercement salt domes, the geologic structure is very complex, resulting in many fragmented reservoirs throughout the fields. 2-D surface seismic surveys and geological data have proven reliable for exploration drilling in these reservoirs. This information, however, is not adequate in defining the small fragmented reservoirs for development drilling. Shooting a 3-D surface seismic survey for each of the fragmented reservoirs usually is economically unfeasible. Traditional vertical seismic profile (VSP) surveys have shown their ability to image complex salt-related structures in complex environments. If the VSP image resolution could be increased to a point where it defines the reservoir near the borehole better than geology or surface seismic could, this would provide valuable information for reservoir development. To be economically feasible, high-resolution VSP imaging must have the capability of being acquired inside tubing and inside casing during workover operations. P. 265^