Reservoir Evaluation For Chang3 Member In Fuxian Exploration Area In Shanxi

Fuxian exploration area in Shanxi province locates in southeast of Shanbei flank belt in Erdos basincovering an area of 3834.51km2 with no fault development in it. Mesozoic section Chang3 in Yanchangformation is an even slope uplifting from west to east gradually and locally developed low relief noseuplift structure. This area is of great exploration potential and has submitted a total reserves of5152.74×104t in interval Chang3. This article focuses on how to determine lithologic traps anddevelopment areas with good porosity and permeability so as to fully use various data and sedimentarytheory to build large scaled model for interval Chang3, summarizes controlling factors of sandbodydistribution, analyzes preserving capability of the reservoir and finally predicts favorable exploration target,which provides geologic basis for next exploration deployment. Main understandings for interval Chang3:(1)Mainly fine sandstone and coarse siltstone, low maturity for component and medium maturity fortexture.(2)It is composed of delta and lacustrine sedimentary environments controlled by northeast sources.Sub facies of delta is better developed while shallow lacustrine facies mainly spreads in the west and southof the exploration area. Distributary channel of the delta is the principle reservoir with sources derivedfrom northeast and nondeveloped sources from south.(3)Total thickness of sandstone is 30-65m, which spreads from northeast to southwest like bandingis controlled by micro facies of distributary channel in delta system.(4)Porosity types of the reservoir: predominantly intergrannular pore, secondly innergranular andintergranular corrosion pore and locally developed fissure with weak porous structure. Diagenesis types:mainly compaction, cementation and dissolution. The former two functions decreased reservoir quality, butinvasion, clay film formation and aedelforsite corrosion improve it, which is the main factor controllingoriginal pore preservation and secondary pore development. Nowadays it is a period of time A,terminal diagenesis for interval Chang3(5)3 types of reservoirs: I (good), II (medium) and III (bad). Lithology is pure for I and II, mainlyfine sandstone;mainly siltstone and lime and mud cemented fine sandstone, generally no oil bearing. I andII are effective reservoirs.(6)Deposition, diagenesis and tectonic movement are the main factors for reservoir developmentand distribution of interval Chang3 with lithologic and structure-lithologic trap as the basic traps. It isready to run rollover exploration for discovered reservoir in interval Chang3. Further exploration targetsare predicted to be Fugu5, Fugu6 well area and Beidaode-Yangquan area.