An integrated approach where information and analysis from each discipline like geology, seismic, petrophysics and reservoir engineering is applied to build three-dimensional (3D) geo-cellular model and finally simulating the reservoir to represent the real flow conditions leading to formulate the field development strategy.
Most of the present workflows are designed to model the clastic reservoirs integrating geological trend and statistical methods effectively. Limestone formations are highly sensitive to fluctuations in temperature, salinity and bathymetry which affect secondary porosity and permeability within the formation and thus result in randomness. Generally, in limestone the integration of geology and geo-statistics is very difficult due to lack of well defined geological trend or randomness. This difficulty is further enhanced if the wells available within the study area are few. Paper brings out how use of seismic derived porosity trend during property modeling led to a meaningful porosity model in a limestone reservoir. In absence of core based J-function data, use of log derived initial water saturation helped in deciding the rock type distribution and saturation modeling capturing the transition zone observed in wells. Classical methods like WOR & WOR derivative plots and material balance study helped in deciding the type of aquifer support and oil volume in place. The paper deals with a real case example of a carbonate reservoir in an offshore environment with around 12 MMT oil in place and 3 exploratory and around 9 development wells within the study area. Finally, with the help of a real case example, the paper brings out the critical stages where the application of integrated approach leads to an improved reservoir model which gives reasonably good estimate of the oil in place and a satisfactory history match.