Locating the Remaining Oil in a Brown Field via Integrated History Matching and Calibration

Abstract Although new discoveries and developments often take the limelight, Brown fields are considered the "backbone" of the oil and gas industry as roughly two-thirds of the world’s daily oil production comes from such fields. A common trend observed with brown fields is that over time, production from these fields progressively decline at the reservoir level because of a combination of factors not limited to declining reservoir pressures, water breakthrough and attendant rise in BS&W and GOR, etc. A critical question which we must answer is: how do we locate these remaining resources and develop them in the most economic manner? This work focuses on conducting an integrated history match and calibration of a brown field reservoirs with a view to identifying and developing remaining oil resources. As a first stage, Well, Reservoir, Facility Management (WRFM) analysis was carried out using classical reservoir engineering techniques to review the field and well historical performance to understand reservoir drive mechanisms and scope for production improvement. Next, a static model was built using seismic data, well logs, mud logs, sidewall samples, core data, RFT data and integrating results from the WRFM. The model was subsequently quality checked initialized and taken into dynamic modeling space. An integrated history matching of the 3-dimensional (3D) reservoir model was conducted first in the reservoir volume (RESV) to quantify aquifer activity followed by oil rate (ORAT) with a primary focus on pressure and saturation as the first stage. This was subsequently followed by calibration using additional information from open-hole and carbon oxygen logs. This provided the required level of confidence in terms of identifying the remaining oil. Finally, different development options were assessed by considering available idle proximal wells for short term oil gains (STOG) and sidetracking. For each development case evaluated, offtake rate sensitivities were also run to arrive at the optimal rate. An additional 1.4 MMstb of oil was realized as the base case from the remaining oil via sidetracking an existing an available idle well.