An Alternative Workflow to Calculate Permeability from the Resistivity Logs and Improve the Flow Unit Definition in the Teak Field, Trinidad Tobago

摘要

Teak, Samaan and Poui (TSP) is a mature field off the South-East coast of Trinidad, which currently produces near to 14,000 bopd with an average Water Cut of 85%. In production since 1972, it peaked at 143,300 bopd in 1978. Repsol E&P T&T has been looking to increase oil recovery by unlocking the remaninig potencial of their reservoirs in Sands 01, 02, 1/2 and 2. An interdisciplinary and detailed study was generated between several disciplines, including geology, petrophysics and reservoir engineering, to re-evaluate these sands, where a waterflooding project had been implemented between the 70's and 90's with seemingly good results. A Static Model was generated starting from a detailed well by well analysis (well logs and core information, seismic, production and pressure data, etc. . .), where some problems, related to uncertantly in the Structural Model and to the interpretation of the input data had to be overcome. This paper explains the workflow that was used to create this static model. First, the originally suspected several Oil Water Contacts (OWCs) had to be analyzed. The area is affected by several fault blocks with varying juxtaposition of the geological layers, which lead to the interpretation, in previous studies, of several contacts. A solution to this and to the effect that this juxtaposition has in the flow within the reservoir and in the pressure distribution is analyzed in this paper. The next step was to reach to a rock type definition based on k/phi relations and a J Function (J(Sw)), with the challenge of having insufficient Core Data and Pc curves. An additional challenge faced was the questionable resistivity logs, which are suspected to have been affected by drilling mud throughout the successive drilling campaigns. Then, in order to define permeability and water saturation models, an alternative workflow was tested and implemented. This method includes conventional rock typing analysis (Pc derived J(Sw)) and extrapolation of these results to the wells. This, together with the resistivity logs (Sw), has been used to compute permeability above the OWC. Threrefore, this allows us to calculate permeability first, and then use it in the J function to calculate the water saturation that will be input into the model. Finally, a Lorenz plot was built to define flow units and identify the possible water injection paths.