Sedimentation And Reservoir Study Of Feixianguan Formation In Longgang Gas Field

As the main exploration horizon in ChuanZhong gas mine, the feixianguan group is one of the major oil and gas series in Longgang gas field, which achieved a great exploration breakthrough in the near future. Thanks to the cores, casting thin sections, the common chip, combining with the fielded profile, papers related chemical analysis and pre-existed researches, the paper studied the formation characteristic of feixianguan group, sedimentary facie, reservoir characteristic and controlling factors etc, divided its types of sedimentary facie into sub-facie and micro-facie, summarized the sedimentary facies model, got the distribution rules of favorable sedimentary facie zones, analyzed the reservoir rock, space type and petrophysical property. As a result, it was determined the type of reservoir, and summarized the characters of the reservoir in the longitudinal and the favorable exploration area.The feixianguan group of Longgang gas field was divided into T1f1, T1f2 T1f3 and T1f4 and composed by five sequences from the bottom to top. Fei ? and ? are the major exploration sequences, the Fei ? included the lower part of T1f1 T1f2 and T1f3, which is consisted by a large sets of clip micrite oolitic dolomite and limy dolomite mainly. Fei ? included the lower part of T1f1, T1f2 and T1f3 which is consisted of large sets of micrite oolitic limestone clip.The sedimentary facies of feixianguan group are mainly divided into 5 facies, which are restricted platform facie, open platform facie, platform marginal facie, slope facie, trough (basin) facies and 8 subfacies,5 microfacies. The platform margin beach facie zone is favorable to reservoir formation and evolution, and the second one is the point beach inner platform, which are distributed in the well area of Longgang 37 to Longgang 30 by a sheet and extended far awayThe reservoir rocks of feixianguan group in Longgang gas field are mainly grain dolomite, residual oolitic dolomite, residual oolitic gray dolomite, dolomite limestone and gray dolomite with dissolved holes. The reservoir space are mainly intergranular dissolved pore and intergranular solution pores, followed by mold hole and gravel dissolved pore. Thanks to the a large number of factures and cavities, it is easy to form pore and fracture-pore reservoir with a character of middle-low porosity and middle-low permeability. On the basis of deposition in the edge and the higher ground of platform, these reservoirs are subjected by atmospheric fresh water, dissolution phase, brief exposure in sedimentary period, dissolution burial period, and fracture communication etc, which improved reservoir capacity and seepage abilityTherefore, Longgang 1-Longgang 28-Longgang 27 well area is the most favorable exploration area, which is located in the platform marginal.