Three-Dimensional Petroleum System Modeling of a Paleozoic Gas Province, Sichuan Basin, China
The greater Tongnanba region, located in the northwest of the Sichuan Basin (Southwest China), is a prolific gas province. However, the area is little investigated and can therefore be considered a frontier area. The hydrocarbon generation, expulsion, and accumulation history in this area is not clear, partly due to the complex tectonic history. We present a fully calibrated three-dimensional petroleum system modeling study for regional evaluation and picking optimal prospects for further exploration.
The Tongnanba area is part of the large intracratonic Sichuan basin and is characterized by platform/basin transition carbonates ranging from Precambrian to Cretaceous in age. The known petroleum systems indicate that most source rocks are of Paleozoic age while the reservoirs are mostly found within Mesozoic strata. Six source rocks of Cambrian, Silurian, and Permian age, and three reservoir rocks of Permian and Lower Triassic age are considered in the study. The known accumulations are thought to be associated with both stratigraphic and structural traps where the hydrocarbons consist mostly of dry gas, derived from now mature to overmature source rocks.
Petroleum system modeling was used in this study to address the objectives mentioned above. For the petroleum system study, calibration of temperature, vitrinite reflectance, and distribution of known hydrocarbon accumulations in three reservoirs has been performed. To calibrate the temperature data, a topography-driven groundwater flow has been considered in combination with a basal conductive heat flow, which resulted in a good match with calibration data.
Based on our results, three of the six source rocks proved to be significant with respect to kitchen area and petroleum generation. The generation, expulsion, and accumulation history was dynamically restored and the most probable scenario has been evaluated based on calibration and sensitivity analyses. The model results match the available geologic data. Furthermore, the study identified three new plays in the study area. Based on these results, auspicious future exploration prospects were proposed. The study provides an excellent example of how petroleum system modeling can aid the understanding of a prospect area, helps to gain more insight to future exploration tasks, and ultimately supports business decisions.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009