Pars Offshore Gas Field Development

Abstract

Abstract Pars offshore gas field is located approximately one hundred and twenty kilometers southwest of the port city of Bushehr in the Persian Gulf (Figure-1). This gas field is being developed by the Oil Service Company of Iran (OSCO) to provide a source of gas for gas injection and gas liquefaction (LNG). Pars gas contains 4.96 Mole percent (Mole%) carbon dioxide and. 6S Mole% hydrogen sulfide. The individual average well production rate is 100Ã?106 standard cubic feet per day (SCFD) at a flowing wellhead pressure of 6500 pounds per square inch (psig) and a flowing wellhead temperature of 270 °F. OSCO is constructing offshore facilities for production and processing of 4.5Ã?109 SCFD of Pars gas. The processed gas will be piped to shore to a 48" injection transmission line at 1800 psig and to an LNG line also at 1800 psig. INTRODUCTION Pars field was discovered in 1965 by National Iranian Gas Company (NIGC) after drilling of the first exploration well DOPCO C-l (Figure 2). During the period 1973–1976 NIGC drilled six additional wells P-l, P-2, P-3, P-4, P-5 and p-6 investigating the Kangan, Upper Dalan, Nar and Lower Dalan formations with the intention of developing a source of gas for liquefaction. Drilling of wells P-4 and P- 5 proved sufficient reserves for NIGC's LNG project and for use in large oil field pressure maintenance projects by OSCO. To optimize operations OSCO tookover drilling activities in May, 1977, and became the sole operator in the area. Early in 1976 as a result of the test of well P-4 it was decided to conduct a feasibility study of the field. The feasibility study indicated that offtake rate of 3.4Ã?109 SCFD was probable, or a maximum offtake rate of 4.5Ã?109 SCFD could be anticipated. Further study indicated that individual average well rates of 100Ã?106 SCFD were possible. Following completion of the feasibility study a second study was initiated to develop an Engineering Plan for development of the field. This study was completed in June, 1977 and is used as the basis for the present development plans for the field. Detailed Engineering Design was started in October, 1977 and is expected to be completed in October, 1978. The design for producing the field is developed in two phases. Phase - I will be for 3.4Ã?109 SCFD rate and with the information gained we will progress to phase-: II at 4.5Ã?109 SCFD. Tables 1,2 and 3 contain the basic information that has been used for well and facility design. At present there are five known geological intervals in the Pars field but number of individual reservoirs is probably only two. The top of the Kangan formation occurs from 8660 feet to 12980 feet, crest to flank, and the Upper Dalan formation occurs from 9295 feet to 13670 feet. It is believed that these two geological intervals will be depleted as one reservoir. The top of the Nar anhydrite occurs from 10230 feet to 12350 feet and is expected to separate the reservoir. The top of the Lower Dalan occurs from 11080 feet to 16300 feet and the top of the Aghar occurs at 12400 feet. The Kangan, Upper Dalan and the Lower Dalan are the primary completion intervals. The Kangan has a bottom hole pressure of 8060 psig and a temperature of 260 °F at 11000 feet. The Lower Dalan has a bottom hole pressure of 8280 psig and a temperature of 286 °F at 14000 feet.