Dynamic Characteristics Of Two-zone Composite Permeability Gas Reservoir Development Studies

Low permeability gas field occupy great position in our country's gas field development. Seeping mechanism and development characteristic of low permeability gas reservoir is different from routine gas reservoir, has many personal characteristic. It is a challenge to exactly know, evaluate and reasonable develop this gas reservoir, which has very important practical meaning for economic and effective developing low permeability gas reservoir.Sulige Gas Field has low porosity, low permeability, low abundance, strong heterogeneity, complicate geological condition and is not very good at effective sand body continuity and connectivity, and so on. It is observed that gas well productivity of this gas reservoir is low, formation energy supply not enough, single well drainable gas is finite. In view of practical problem during Sulige gas field development, this paper complete follow study content. Study material balance theory of two district compound gas reservoir. Carry out stress sensitivity experiment on matrix rock and labor created fracture core from Sulige gas field with America Core Company high pressure high temperature flow experimental instrument to study stress sensitivity change rule of different permeability matrix rock and created fracture core at the condition of time and again switch on and off well and different drawdown pressure. Carry out depletion experiment on matrix rock of different permeability serial combination with different kinds of allocation, using double core clamper serial connected experimental apparatus, to study gas well production performance of bi-zonal compound low permeability reservoir during low pressure production stage. At the basis of experimental study, establish single well simulation model to analyze development index infection caused by stress sensibility and production performance infection rule caused by inner formation and outer formation of bi-zonal compound gas reservoir permeability variation while considering stress sensitivity.Main study achievement generalize as follows:·Core stress sensibility of Sulige gas field is strong, matrix rock permeability fell extent at 10%~45% caused by stress sensibility. Core permeability gradually decrease along with increase of effective stress fluctuate times or switch on and off well times, drop to limit value when fluctuate times enough. Core permeability decrease more with drawdown pressure greater.·Core stress sensitivity change rule of labor created fracture has same characteristic with matrix rock that permeability relative value fall extent at effective stress increase early stage is greater than late stage, created fracture core permeability decrease about 60% at 25MPa drawdown pressure. Therefore, it is very important to control drawdown pressure when fracture reservoir produce.·Serial connection experimental model of bi-zonal compound reservoir with depletion exploitation, pressure drawdown rule is as flow: pressure of relative high permeability and relative low permeability district decline rate at early stage is more quick than at late stage, pressure decline more quick with higher allocation, when allocation access a certain extent, pressure decline without apparent change, pressure of near well relative high permeability zone decrease more quick with the permeability of peripheral low permeability zone more low, while pressure of low permeability zone decline relative slow and abandonment pressure high. Output change rule is as follow: output of relative high permeability zone is larger than relative low permeability at the period of stabilized production, bi-zonal production variance is more apparent with allocation higher, gas is mainly produced by near well relative high permeability zone. Output of near well relative high permeability zone decline quick while output of relative low permeability zone decline relative slow at the production decline stage, low permeability zone gas produce apparent.·Numerical simulation indicate that productive capacity of peripheral low permeability zone for gas well is not be sneezed. Increase near well formation permeability, cut economic limit rate, prolong low pressure and low production stage to raise gas recovery of peripheral low permeability zone and improve single well recoverable reserves and raise gas well ultimate recovery. These are efficient paths to economic and effective develop bi-zonal compound low permeability gas reservoir.