Integrated 3D reservoir-modeling at Ram-Powell field: A turbidite reservoir in the eastern Gulf of Mexico

Abstract

Abstract Ram Powell is a stratigraphically trapped sequence of turbidite reservoirs in 2,500-4,000 ft of water in the Eastern Gulf of Mexico. The discovery was made in 1985 and the field has been the subject of extensive geoscience and engineering studies. In spite of this work there is still significant uncertainty in Ram Powell reserves. The Ram Powell development plan is underway, with fabrication of a tension-leg platform and 60,000 b/d plus 200 MMcf/d facility. Drilling will include 7 high rate horizontal wells and 3 water injection wells. Reserves accessed in this development scheme are approximately 250 million barrels equivalent. Model-based seismic inversion (constrained by 12 appraisal penetrations, rock property data and seismic interpretation) was employed over the main reservoir interval (J, L and N sands) to create models that are consistent with 3D seismic data. These models were used in several simulation studies including element models to determine optimal well placement, and full-field models to predict overall reservoir performance. The results of the study both reduced and enabled management of reservoir volume uncertainty; they were critical for determining the number, horizontal length and placement of wells (vertically and areally). The results also provided the basis for a proposal to increase the facility capacity limits to 70,000 b/d plus 260 MMcf/d. Some significant learnings are (1) model-based inversion is now in a production mode that can be rapidly applied to reservoir problems, (2) many reservoir complexities are simply below seismic resolution and inversion is unable to add with certainty significantly more resolution and, (3) detailed reservoir models that reflect reservoir conditions and are easily manipulated are required for reservoir optimization. Introduction Purpose. The Ram Powell Field is currently under development with fabrication of a tension-leg platform and 60,000 b/d and 200 MMcf/d production facility. Development will include 7 high rate horizontal wells and 3 water injection wells with a single subsea well drilled much later. Production is scheduled to begin in August, 1997 and the expected reserves are 250 million barrels equivalent. The purposes of this paper are (1) to describe the process used to integrate 3D seismic, geological, and rock property data into a static model that was used for reservoir simulation, (2) to illustrate how the modeling was used to manage uncertainty, and (3) to illustrate the impact of this work on development planning and facility design. Setting. Ram Powell is a stratigraphically trapped sequence of turbidite oil and gas reservoirs in 2,500-4,000 feet of water in the eastern Gulf of Mexico. The discovery was made in 1985 and has had extensive geoscience studies performed since then by each of the Ram Powell joint venture partners. A fairly extensive set of data is available including three 3D seismic surveys, twelve wells (drilled from five surface locations), 420 feet of conventional core, one production test, in addition to the normal set of petrophysical logs, RFT's, and sidewall samples (Figures 1, 2 and 3). In spite of the extensive data set, uncertainty remains with respect to Ram Powell reserves. Uncertainty in reservoir limits, net thickness, effective permeability (vertical and horizontal), fluid properties, well placement, and well design all have an impact on reservoir performance prediction (rate and cumulatives). There are three reservoirs in the initial development phase (J, L, and N sands). P. 477