Adapting Field Development Plan of Compartmentalized Oil Rim Reservoir with Significant Gas Cap and Water Aquifer - Case Study

Abstract

The paper is continuation of SPE-177659, This work illustrates adapted field development plan and optimization studies conducted on a Middle-Eastern compartmenlized complex carbonate oil rim reservoir with significant gas cap and water aquifer. The need to expedite the field development was realized based on increasing gas demand for the country as well as fast pace of urbanization in area which can potentially complicate the field development in future with regard to availability and accessibility of drilling sites. The surrounding fields have seen ranges of H2S concentartion in compositionhence, public safety is a major concern. PVT studies indicate a wide range of compositions which further complicates the development plan considering the surrounding sensitive environment. The reservoir exhibits relatively fair to poor reservoir characteristics, variable contacts and composition variation across the reservoir due to faulting- suggesting the presence of multiple reservoir compartments. To exploit the sweet spots of a thin oil rim in highly faulted reservoir is a major challenge considering limitation on drilling location and horizontal reach. The scenarios of field development and economics were created for developing the reservoir as oil as well as gas development. A total of 10 wells had penetrated the reservoir out of which 8 wells tested oil and suggested a significant initial gas cap while 2 others penetrated water leg. Six years of early production scheme (EPS, 4 producers, 1993 to 1998) data in addition to production testing, core (2 wells), MDT (3 wells), PVT (4 wells) data were gathered in order to identify the main uncertainties and test the feasibility of the full field development. EPS indicated production decline coupled with severe increase in GOR and water cut in some wells, after which the producing wells and facilities were P&A due to safety concerns and low productivity. A number of parameters were addressed and optimized as a part of full field development plan. The dynamic modeling suggests that an ultimate recovery of 70% can be achieved by the different injection scenarios. However, considering the complexity of the surrounding environment and the size of the prize, it is recommended that the field development should be consideredfor a period of 10 years under natural depletion considering economically viability, provided the most effective development strategy in terms of number, location, orientation and horizontal reach is adopted. Initially it was planned to develop the field as oil rim development however the development strategy was adopted to develop the gas cap instead of the oil rim considering urgency of development, low oil price forecast in short term, better economics and the country gas demand. This work discusses the influence of different parameters including the human landscape on decision making.