A COMPREHENSIVE CONCEPTUAL STUDY FOR ECONOMIC DEVELOPMENT OF THE OIL FIELDS IN KAILASHTILA AND HARIPUR

Abstract

Bangladesh occupies major part of the Ganges delta Basin and has been known as a natural gas rich province. However, occurrences of oil have been known in two small oil fields, Haripur and Kailashtila. While Haripur, discovered in 1986 was on production for six years, Kailashtila, discovered in 1988, was never put under commercial production. Energy experts recommend that development of the two discovered oil fields should be carried out. This process requires preparation of oil reservoir development plans, procurement of equipment and development of skilled manpower. Oil production data and record of six years of operation in Haripur oil field and oil flowing record during drill stem test operation in Kailashtila field have testified the production capabilities of the oil reservoirs in the fields. The present study suggests that the oil development works in these fields are terminated not because of depletion of reserves but because of not following the right procedures of the oil field development. In this study an effort has been made to prepare oil reservoir development plans on the two prospective oil fields. Comprehensive study on every aspects of oil reservoir such as seismic section, well logs, well test, core analysis, fluid analysis, fluid contacts leads to preparation of technically feasible and economically viable oil reservoir development plan. Oil reservoir development plan includes reservoir simulation models with defined oil recovery mechanism, optimum number of oil production wells, optimum number of water injection wells and mutual positions of wells in reservoir. Finite difference reservoir simulation model (conventional reservoir simulation model) and streamline reservoir simulation model are developed from seismic section, well logs, core analysis, fluid analysis, well test, drill stem test, fluid contact and production history. Oil recovery mechanism is optimized from analysis of reservoir pressure, rock properties, fluids properties and core flood test. Streamline simulation study is performed to optimize number of oil production wells, number of water injection wells and mutual positions of wells in the reservoir. Oil production rate, well head pressure, water injection rate, water injection pressure and production period are also defined in oil reservoir development plan. Finite difference reservoir simulation study is performed to optimize oil production rate, well head pressure, water injection rate, water injection pressure and production period.

Finite difference reservoir simulation model and streamline reservoir simulation model have been constructed on oil reservoir in Haripur field. Then the oil reservoir models are validated by history matching with six years oil production data available. The reservoir has been screened to design enhanced oil recovery technique. Low salinity water (salinity 1000 ppm of NaCl) injection method has been recommended for oil reservoir to recover remaining oil. On the basis of oil recovery technique reservoir development variables have been optimized to generate reservoir development scenario. The oil reservoir has been proposed to develop with six water injection wells and two oil production wells. Streamline simulation has been run on the reservoir development scenario and observed the performance of the reservoir such as hydraulic conductivity, oil flow rate, oil flow direction, water flow rate, time of flight, water break through, water channeling and sweeping efficiency. The Haripur oil reservoir has shown good performance under the development scenario. The reservoir model with the optimum development scenario has been considered as reservoir development plan. The optimum reservoir development plan has been simulated by finite difference reservoir simulator for duration of twenty years for economic analysis of the development plan. Haripur oil field initially had 33 million barrels of oil and produced 0.53 million barrels of oil. Experts have predicted that there is remaining oil in the reservoir which is approximately 32.47 million barrels of oil. Six injection wells are used for water injection. Water injection pressure is 1000 psi. Well water injection rate is 300 stb/day and field water injection rate is 1800 stb/day. Two oil production wells are used for oil production. Well oil production rate is 400 stb/day and field oil production rate is 800 stb/day. Well head pressure of oil production well is 500 psi. Total oil recovery is about 5.844 million barrels within twenty years from Haripur field. Break even oil production is 2.044 million barrels of oil. Conventional and streamline reservoir simulation models of oil reservoir in Kailashtila field have been constructed by using seismic survey, well logs, core analysis, fluid analysis, fluid contact data and drill stem test data. Reservoir simulation models have been validated by oil production data from drill stem test operation. As the oil reservoir has significant pressure to lift oil to the surface as detected from drill stem test, natural depletion mechanism has been proposed to recover oil from reservoir. A single oil production well has been placed at the center of the oil reservoir in Kailashtila field for oil reservoir development. Streamline simulation has been run on the reservoir development scenario and observed the performance of the reservoir such as hydraulic conductivity and oil flow rate. The Kailashtila oil reservoir has shown good performance under the development scenario. The Kailashtila oil reservoir model with the optimum development scenario has been considered as optimum reservoir development plan. Twenty years oil production has been forecasted from the oil reservoir development plan by simulating the finite difference reservoir simulation model of Kailashtila oil reservoir. Experts have predicted that Kailashtila oil field initially has 94.33 million barrels of oil. A single oil production well is used for oil production. Well oil production rate is 817 stb/day. Well head pressure of oil production well is 500 psi. Total oil recovery is 5.973 million barrels from Kailashtila field. Break even oil production is 0.584 million barrels. The oil reservoir in Kailashtila field is able to produce 0.129 million barrels of additional oil than Haripur oil reservoir because Kailashtila oil reservoir contains lighter oil (42 oAPI) and Haripur oil reservoir contains heavier oil (28.5 oAPI). In this study maximum effort has been done concentrated in seismic and well logs interpretation as well as laboratory test to minimize data uncertainty for preparing reliable oil reservoir development plans on Haripur and Kailashtila fields.