A Comprehensive Evaluation of the Dover 7-5-VE Trenton-Black River Field

摘要

Detailed geological, geophysical and production analysis of the Dover 7-5-VE field suggests that it is comprised of at least three distinct reservoirs, two Trenton gas reservoirs oriented east-west and a main Black River oil reservoir oriented northeast-southwest. Overlaying the Trenton time horizon with the production data supports the hypothesis that Ordovician structures define compartmentalized reservoirs. Interpretation of the 3-D seismic top Trenton surface shows the development of pod-like or chimney-like structures within all three trends. Comparison of the Trenton time horizon with an analogue model for pull-apart basins reveals the major components that are most readily identified on both 2-D and 3-D seismic. The major features include terraced fault blocks that are present within the main part of the structure, a (transecting) cross-structure fault that runs the entire length of the pull-apart structure, and inactive structures or fault splays along the margins of the pull-apart structure. At either end of the pull-apart structure we observe expressions of a negative flower structure and an in-line graben. The Dover 7-5-VE field is a negative flower expression in the Trenton-Black River carbonates of southwestern Ontario created by sinistral shearing. Support for the development of the reservoir model included extensive petrography, geochemical and burial history modeling of the Trenton-Black River carbonates within southwestern Ontario. There have been several stages identified in previous studies but the three main stages include Stage 1 -Dolomitization (reservoir creation), Stage Ⅱ -Hydrocarbon emplacement and hydrothermal alteration, and Stage Ⅲ Final shearing and fluid remobilization. These stages summarize the major events and account for many of the features encountered during drilling of Ordovician wells as well as visualized on seismic within southwestern Ontario.