Research On Shallow Gas Reserves Evaluation In Lamadian Oilfield

Shallow gas in Lamadian Oilfield is the gas-bearing reservoir in Sa0 group and N4 member to Quaternary layer, and can be divided into Sa0 group and shallow gas bearing formation. In 1968, by testing for gas in well La174, it proves that Sa0 group has natural gas resource. In 1973, during the time when Lamadian Oilfield develops in full scale, drilling data proves that shallow gas exist indeed. Because of the oilfield development plan's limited, research for shallow gas is only in preliminary. However, with everlasting development for oil field, extra high water containing time emerges, and remains recoverable reserves decrease increasingly, contradiction between reservoir and recovery intense more and more, high and stable yield turns difficult. In order to apply oilfield development plans that supplement oil by gas, and ensure oil field can be of sustainable development, research on shallow gas reserves evaluation in Lamadian Oilfield is preceded.In this paper, at first, by researching geologic characteristic of Sa0 group, it draws dividing method for bed set and electronic logging standard for gas bearing sand thickness, and constructs faults distribution map, structural map, isopach map and sedimentary facies map of Sa0 group, and defines depositional environment and reservoir nature. Secondary, by researching gas bearing formation reserves parameters in Sa0 group, it defines gas bearing sand thickness, oil-gas interface, gas bearing area, porosity, gas saturation and volume conversion factor etc. parameters, calculates and evaluates gas reserves in Sa0 group.Researching result indicates that①by using cycle-comparison and step control method for dividing bed set, Sa0 reservoir can be divided into 8 sublayer compared to old 3 member, and new result is more reasonably for development of Sa0 group.②Sedimentary facies of Sa0 reservoir is entirely delta front facies deposition, and the reservoir is mainly sand sheet with banded, block sand sheet in the small. Gas bearing sand is of 3 types, which are scattered for Sa0 clip, belt for Sa01 and Sa04 and steady for Sa02, Sa03, Sa05, Sa06, Sa07, Sa08.③Sa0 reservoir belongs to middle part oiliness array, and it has united oil-gas interface and oil-aqueous interface with lower reservoir, oil-gas interface depth is -770m.④Gas bearing area of Sa0 reservoir is 53.1Km2, gas in place is 31.05×108m3, reserves abundance is 0.58×108m3/km2, sustained gas daily output in kilometer well depth is 1.9×104m3 /km.d, and it belongs to low yield, low abundance, and middle-sized shallow layer gas pool with drip ring.