Steam-Flood Trial and Research on Mid-Deep Heavy Oil Reservoir QI40 Block in Liaohe Oilfield

Abstract

Abstract In the paper, the implementation process and results of the pilot tests and expanded tests of steam drive in Block QI40 in Huanxiling Oil Recovery Plant of Liaohe Oilfield is analyzed, the patterns and production features of steam drive in moderately deep, medium ∼ thick interbedded conventional heavy oil reservoirs after steam huff and puff are studied and the supporting technologies developed during the steam drive in Block QI40 are outlined together with the problems solved by the technologies. Valuable knowledge and experience have been obtained in terms of heavy oil steam drive in moderately deep formations. At the same time, it has been proved that satisfactory development results and reasonable economic benefits can be obtained when steam drive is applied to the moderately deep heavy oil reservoirs after many cycles of huff and puff, providing reliable operational experience and technical support for the commercialization of steam drive in Block QI40 and similar oilfields. Reservoir geological situations of Block QI40 Block QI40 is situated in the middle section of the west slope of the west depression in Liaohe Basin. The target formation is the Lotus formation of lower S3 and it is a fan shaped delta front facies deposition. The reservoir is mainly made up of medium to fine sandstones, and silty fine sandstones with 6.04% clay minerals. The reservoir rocks are unconsolidated, being mainly porous cement. The Lotus formation is divided into two sub groups, Lotus I and Lotus II, which have the same oil/water contact with the depth of -1040∼-1050m. The oil/water relationship is simple with the upper part of the structure being the pure oil zone and the lower part water zone. The oil layers are well separated, providing favorable conditions for separate layer development. The burial depth of the Lotus formation ranges from -625 to -1050m with concentrated well intervals with the length of 70 to 150m. The oil formation is thick with the average effective thickness of 36.03m and the average net /gross thickness ratio of over 0.50. The Lotus formation is a typical moderately deep, medium to massive laminated structural lithologic conventional heavy oil reservoir with edge water and high porosity, high permeability. The average porosity and permeability are 31.5% and 2.062´10–3µm2 respectively1. Table1 and table 2 show the reservoir parameters of the Lotus formation and Fluid properties of the Lotus formation in Block QI40. Heavy oil steam drive patterns and production features in moderately deep formations Brief introduction to the steam drive test Block QI40 was put into steam huff and puff development in 1987. In Oct.1998, steam drive pilot tests were started in 4 well groups and the tests were expanded to another 7 well groups in July 2003. Right now, the whole block is being converted into steam drive development. The steam drive pilot tests were targeted at Lotus II formation group with the burial depth of -924m. The formation group has good communication and uniform vertical physical properties. Before the tests, steam huff and puff had been conducted for 7.7 cycles averagely in 9 of the existing wells in the pilot area. Before converting to steam drive, the average residual oil saturation was 0.57 and the average formation pressure was 3∼4Mpa and the recovery was 24%. The expanded 7 well groups were situated to the west of the pilot tests and the target zone remained the same, i.e.(Fig.1.) The reservoir conditions were generally similar to those in the pilot area with only the formation thickness being less. Before steam drive, there were 36 wells in the area with altogether 209 cycles of steam huff and puff and the recovery of 29% and formation pressure of about 2MPa. The residual oil saturation was 0.53 when steam drive started.