The Determination Of Optimal Re-fract?ring Timing In Tight Oil Reservoir And Its Effect Prediction

As a key technology of enhancing tight oil well production,the re-fracturing process plays a very important role in the exploitation of tight oil.In the prod uction process of tight oil well,reservoir or fracturing technology may cause hydraulic fracture fail gradually and production reduce.To recover single well productivity,it is necessary to re-fracture oil well,aimed at reopening failed fractures or fracturing new fractures.Optimal re-fracturing timing and optimization of re-fracturing parameters ensure improving re-fracturing economic benefit and carrying out related study of them can provide theoretical and technical guidance for field design.Aiming at re-fracturing candidate wells selection,the paper analyzes the factors which influence re-fracturing effect of tight oil well from two aspects containing static indexes and dynamic indexes.Based on the establishment of decision s upport database,the re-fracturing decision-making method is established by combining fuzzy comprehensive evaluation and analytic hierarchy process and the potential candidate wells are selected preferentially.Based on the well selection,the mathematic model of prod uction prediction considering threshold pressure gradient and fractured fracture conductivity failure is established.Then the paper divides flow period of tight oil production process and analyzes prod uction effect factors.On the basis of analyzing the pressure and production performance curves,when the prod uction performance curve before re-fracturing reaches system radial flow period,the fract ured fracture loses high flow cond uctivity and production of oil well restores to level before re-fracturing,then the time when system radial flow appears is the optimal re-fracturing timing.Based on the inverse problem of prod uction performance prediction model of tight oil well,the thesis comes up with method of reservoir and fracture parameter inversion on the basis of Bayesian inversion method,which proves to have more advantage over that on the basis of GA.Finally,Based on the geological and develop ment data of fractured wells in Z field,the thesis carries on re-fracturing well selection,the determination of optimal re-fracturing timing and re-fracturing effect prediction in oil field application.By contrasting the predicted production with the real production,the paper suggests the research result could provide theoretical guidance for highly efficient construction in field.