Commissioning and Operational Experiences of Java Seawater Treating Facility

Abstract

Summary This paper summarizes the design, commissioning, and operational experiences of Pertamina/ILAPCO's Java seawater treating facility in the Southeast Sumatra Contract Area. Commissioning problems such as deaeration by gas containing 20 mol% CO2, mitigation of bacterial contamination, and water quality/suspended solids measurements are reviewed. The effects of radical pH depression on biocide requirements, corrosion rates, and oxygen seawater requirements are examined. Introduction Pertamina/ILAPCO's seawater treatment facility for Pertamina/ILAPCO's seawater treatment facility for pressure maintenance/secondary recovery of the Rama pressure maintenance/secondary recovery of the Rama field reservoir is located on Pabelokan Island. Pabelokan Island, in the Thousand Islands chain, is approximately 7 miles [11.3 km] southeast of the Rama field and approximately 55 statute miles [88.5 km] offshore and northwest of Jakarta, in the Java Sea. In Nov. 1975, crude production from the Rama field began with the Rama A satellite platform. Rama field development has continued through March 1983, with current production from nine Rama satellite platforms. A Rama reservoir model study, completed in 1980, indicated that recovery by natural depletion would approximate 80 million bbl [ 12.7 × 10 6 m3 ] of oil, or 13 % of the estimated oil in place. The study further indicated that pressure maintenance could increase recoverables by 80 pressure maintenance could increase recoverables by 80 million bbl [ 12.7 × 10 6 m3 ]. Pressure maintenance began during the last quarter of 1982, with injection into nine wells at a total rate of 200,000 B/D [31 797 m3/d] water. Suspended solids content of the treated seawater has averaged 0.01 mg/L. Water of this quality, when applied to the Barkman/ Davidson' formulas, gives an injection half-life of 6.5 years. Water Quality Requirements Millipore filter studies applied to the Barkman/Davidson equations and published laboratory/field experiences of other operators were used in developing water quality specifications. Of particular importance were injection studies done in the Brent and Forties fields of the North Sea, 2 because of similarities in seawater mineral content and reservoir permeabilities. (See the review of seawaters worldwide in Table 1.) The Rama field reservoir is composed of three limestone facies:the Lower Batu Raja (LBR) reefal,the Lower Batu Raja (LBR) marine, andthe Upper Batu Raja (UBR) reefal. Eight of the nine injection wells are completed in the UBR. Porosity of the UBR averages 23 %, with permeability ranging from 7 to 95 md. The LBR, with one permeability ranging from 7 to 95 md. The LBR, with one injection well, is of leached vuggy porosity and is highly fractured, with a porosity of 21 % and permeability ranging from 5,000 to 2 md. Java seawater was tested for solids content and plugging tendency by using Millipore filters. During the test plugging tendency by using Millipore filters. During the test procedure, 0.45 m Millipore filters were used. The procedure, 0.45 m Millipore filters were used. The filters have a calculated permeability of 14 md, which is the approximate mean permeability of the Rama field reservoir. The filter cake that forms on the Millipore membrane filter can be directly related to the filter cake that forms at the formation face and within the formation. The permeability of the filter cake is correlated, by mathematical formula (Barkman and Davidson), to the permeability of the formation, and an injection half-life permeability of the formation, and an injection half-life is calculated. Water Treating Facilities The Pabelokan treating facility was custom designed to provide water quality with a maximum suspended solids provide water quality with a maximum suspended solids content of 0.2 mg/L and removal of 95 % of all solids mu m and greater, as determined by injectivity calculations. The treating facility consists of eight major components, described in the following paragraphs. (For facility layout see Fig. 1.) Seawater Intake Sump The seawater sump, located on Pabelokan Island, is a V-shaped, concrete-reinforced Pabelokan Island, is a V-shaped, concrete-reinforced structure approximately 26 ft [7.9 m] deep, and is designed to handle 240,000 B/D [38 157 m 3 /d] water. Raw seawater is fed into the intake sump through a 36-in. 10.91-m] siphon line, which extends approximately 300 ft [91.4 m] offshore, with the inlet 65 ft [19.8 m] subsea. Hypochlorite Generator Hypochlorite, or chlorine, is injected at two locations:the inlet of the 36-in. [0.91 -m] siphon line, to prevent the buildup of crustacea, andat the seawater intake sump. The treating facility has two hypochlorite generators, one for 100% standby capacity. JPT P. 1276