The Reservoir Character Of Upper Shaximiao Formation In Luodai Area Of West Sichuan Study

Luodai gas field lies in central section of West Sichuan Sag. There are about 20 km away from east Chengdu.It is a unwonted"city gas field"in our country. Upper Shaximiao Formation is one of the most gas production-layer.The roll-exploration and exploiture of the gas field has been limited because of low study-degree, compact and nonuniformity and complicated forming mechanism.The study of reservoir of upper Shaximiao is imptante,we can find out distributing, evolvement storage of the reservoir by it.It can supply scientific gist of exploration and disposing.The deposition of upper Shaximiao Formation in Luodai area of West Sichuan belongs to delta regime under the condition of arid climate and oxidation. the reservoir of this area have the character of low porosity, low permeability, compact and nonuniformity because of much stage tectonic cycle, abidance subsidence and diagenesis diversity in this area.Sand body develops vertically far and wide, taking the form of podiform or silllike. And the distribution of sand body lies north to east or south to north closely in plane, restricted by sedimentary environment. The favorable sedimentary facies are distributary channel under water and outfall dam. Through this research, the diagenesis sequence of upper Shaximiao Formation is set up and the constructive diagenesis is mostly concentrated in middle part of target stratum, which is signed by chlorite develops..Groundwater distributes in the reservoir of upper Shaximiao Formation widely. It,s mineralized degree is higher than other areaes. The type of the groundwater is CaCl2. The groundwater is relative close to the forming of the gas,the relation of the gas and groundwater is complex,it has a of mixwater.Groundwater which is mostly residual water and gas exist to the same reservoir,they have a same pressure system,forming and coming out with gsa,having no side-water and bottem-water ,lacking durative supply.At the same time, the groundwater of reservoir is relative close to sedimentary facies and porosity. Usually, the water character of the sand bodies with biggish thickness and good porosity is much more obvious.The reservoir of upper Shaximiao Formation is divided into 4 types by reservoir lithology, porosity, permeability and pore structure. Among them ,theâ… ,â…¡type are the main goal of exploration.On the study of deposition, diagenesis and reservoir quality, through reservoir identification and tracing, the response character of physical geography of available sand body is set up and the distribution of available reservoir is predicted, the exploration goal in future is put forward.