The first full scale steam drive in Mount Poso Field began in 1971. Additional steam drive projects were begun in 1974, 1976, and 1977. All of the Upper Vedder reservoir in the main part of the Mount Poso Field is under steam drive. Oil production from the field is currently 13,000 barrels per day. This compares to extrapolated primary decline of 1700 barrels per day. per day. A thermal reservoir simulator has been used to determine the effects of various operating policies. Eliminating steam entry into the policies. Eliminating steam entry into the producers is the most significant process improvement producers is the most significant process improvement found. The mid field producers are the wells which recover most of the oil. The effect of losing one of these wells is shown.
A thermal simulator has also been used to optimize the design of a steam drive in the largest remaining portion of the field. Pumping policy and the quality of injected steam have been investigated. The thermal simulator has helped us lay out an integrated engineering plan for the steam drives in Mount Poso Field.
The Mount Poso Field is located approximately 14 miles north of Bakersfield, California. The field is six miles long and up to one mile wide. There are three main pay zones, the Upper Vedder, Lower Vedder and the Third Vedder. The reservoir dips 6 degrees to the west and is closed on the east by the Mount Poso Fault. There is a strong waterdrive in each of the zones. Figure 1 is a structure map of the Upper Vedder zone. The east-west extent of the Lower Vedder oil bearing sands is about half that of the Upper Vedder. The east-west extent of the Third Vedder oil bearing sands is about a quarter of the Upper Vedder. There is sand-to-sand contact across the faults in the downdip, central part of the field. Pressure data indicate these faults are partial barriers to fluid movement.
The pattern for steam injection was determined from physical model studies. It consists of a row of steam injectors downdip just above the original oil-water contact and a row of steam injectors updip. The process is steam drive from the updip injectors. Steam is injected into the downdip wells for two to four years to heat the downdip area. This heating is designed to prevent the formation of a cold oil bank.
Stokes et. al. described the operation of the steam drive projects in the Mount Poso Field. Stegemeier et. al. described vacuum models and their application to Mount Poso conditions. This paper presents the use of numerical reservoir simulators presents the use of numerical reservoir simulators to determine optimum operating policies for the Mount Poso Field.
PRIMARY DEPLETION HISTORY MATCH PRIMARY DEPLETION HISTORY MATCH Previous engineering work on Mount Poso was primarily concerned with project feasibility and basic process design. A simplified picture of conditions at the beginning of steam injection was adequate for these purposes. Since the current study addresses problems of a more specific nature, a more detailed description of reservoir conditions at the start of steam drive was required. The most important simplifications used in the previous studies were those of a uniform initial oil saturation and a constant pressure or constant water influx rate at the downdip boundary of the prototype. These simplifications have important effects on process optimization. process optimization. In order to obtain a more detailed description of initial conditions at the start of steam injection, it was decided to history match the field average primary depletion of the Upper Vedder, Lower Vedder, and Third Zone for a prototype strip along dip using an isothermal implicit reservoir simulator. The basic reservoir and fluid properties of this prototype are listed in Tables 1 properties of this prototype are listed in Tables 1 through 5. The capillary pressure curves shown in Figure 2 were used. These curves were obtained from laboratory analyses of core samples.