Pore pressure prediction using 2D Basin modeling technique

Abstract

Overpressure and underpressure in the basin are mainly developed due to the disequilibrium compaction between the pore fluids and overburden pressure, and the heat flow/geothermal gradient in the rocks, leading to serious hazards in drilling operations due to the catastrophic well blowouts. Although some techniques have been used to explain the pore pressure mechanisms, there are still some missing gaps in the prediction. Basin modeling software is a very powerful tool as it incorporates various physical phenomena and can simulate the geological history of a sedimentary basin. Thus, a two-dimensional basin modeling software – TemisFlow, was used in the study. The present study was conducted at the Pelotas Basin, Brazil with the aims of (1) to build and run scenario test for pore pressure prediction of the Pelotas Basin, Brazil, (2) to identify the factors that control the pressure development, (3) to test the sensitivity of the parameters that control the pressure distribution, and (4) to evaluate the pressure distribution and pattern in the study area. The temperature model simulated by the software is calibrated with the field data provided in the well log as field pressure data is not provided. Nevertheless, calibration still can be done as the temperature at present and during the basin evolution is one of the parameters to pressure calculation in the model. Generally, the results show abnormal pressure zones are developed only in lower permeability of lithology – shale. Based on the simulations scenarios tested, the presence and generation of hydrocarbon in the Pelotas Basin also contribute a little to the development of overpressure in the basin. Based on the basin modeling results, the main overpressure mechanism in Pelotas Basin is still mainly due to compaction disequilibrium.