| Fracture-cave type carbonate reservoir has a important position in oil and gas field development at home and abroad for its reserves and production proportion reachs50%-60%. The research of fluid seepage property in matrix and fracture and seepage mechanics property in cave is a dynamical foundation of fluid flow feature in fracture-cave type carbonate reservoir, only reflecting flow feature correctly of fluid in fracture-cave type carbonate reservoir can provide correct theory guidance for well testing in fracture-cave type carbonate reservoir. Current well testing research in fracture-cave type carbonate reservoir is based on multiple porous model, wherever how big cave scale is and if cave distribution is relatively continuous, the mathematics model which reflects dynamical behavior of whole fracture-cave type reservoir just only generalized from double porous to trible porous, still treated as multiple porous concept. Development practice for many years at home and abroad has formed comparatively ripe technique and matching technology, at the same while formed a series analysis methods which based on double porous carbonate reservoir, such as conventional method、well testing method、numerical simulation method and so on. BEM is applied in various engineering sciences widely, but a few research reports in oil and gas seepage theory and well test theory. BEM application in oil and gas seepage theory and well test theory mainly is solving unsteady pressure under stable production, production decline law under stable pressure was not reported. Based on the previous research,the fracture-cave type carbonate reservoir mathematics model was established, well bottom pressure changing rules under stable production and well production decline law under stable pressure were studied by Laplace transform and BEM, numerical calculating method of investigation radius and abnormal point distance were given, finally the established double logarithm chart was applied in carbonate reservoir of an oil field.Main achievements including:(1) Taking wellbore storage factor and skin factor effct in consideration, the mathematics model of carbonate reservoir with part impermeable zone producing at stable production was established firstly, the Laplace space mathematics model was obtained subsequently by dimensionless conversion and Laplace transform, then the BEM linear equations were derived by BEM. Finally the parameters influence on well bore pressure were studied, the parameters include part impermeable zone distance from well、size of part impermeable zone、fracture interporosity flow coefficient、storage properties ratio.(2) Taking wellbore storage factor and skin factor effct in consideration, the mathematics model of carbonate reservoir with part composite zone producing at stable production was established firstly, the Laplace space mathematics model was obtained subsequently by dimensionless conversion and Laplace transform, then the BEM linear equations were derived by BEM. Finally the parameters influence on well bore pressure were studied, the parameters include part composite zone distance from well、size of part composite zone、fracture interporosity flow coefficient、storage properties ratio、composite zone flow ratio.(3) Taking wellbore storage factor and skin factor effct in consideration, the mathematics model of carbonate reservoir with nearby cave producing at stable production was established firstly, the Laplace space mathematics model was obtained subsequently by dimensionless conversion and Laplace transform, then the BEM linear equations were derived by BEM. Finally the parameters influence on well bore pressure and cave pressure were studied, the parameters include cave distance from well、 size of cave、fracture interporosity flow coefficient、storage properties ratio.(4) Taking wellbore storage factor and skin factor effct in consideration, the mathematics model of carbonate reservoir with drilling cave producing at stable production was established firstly, the Laplace space mathematics model was obtained subsequently by dimensionless conversion and Laplace transform, then the Laplace space analytical solution was solved. Finally the parameters influence on well bore pressure were studied, the parameters include size of cave、cave interporosity flow coefficient、fracture interporosity flow coefficient、storage properties ratio.(5) The mathematics model of carbonate reservoir with part impermeable zone producing at stable pressure was established firstly, the Laplace space mathematics model was obtained subsequently by dimensionless conversion and Laplace transform, then the BEM linear equations were derived by BEM. Finally the parameters influence on production decline curve were studied, the parameters include part impermeable zone distance from well、size of part impermeable zone、fracture interporosity flow coefficient、storage properties ratio.(6) The mathematics model of carbonate reservoir with part composite zone producing at stable pressure was established firstly, the Laplace space mathematics model was obtained subsequently by dimensionless conversion and Laplace transform, then the BEM linear equations were derived by BEM. Finally the parameters influence on production decline curve were studied, the parameters include part composite zone distance from well、size of part composite zone、fracture interporosity flow coefficient、storage properties ratio、composite zone flow ratio.(7) The mathematics model of carbonate reservoir with nearby cave producing at stable pressure was established firstly, the Laplace space mathematics model was obtained subsequently by dimensionless conversion and Laplace transform, then the BEM linear equations were derived by BEM. Finally the parameters influence on production decline curve and cave pressure were studied, the parameters include cave distance from well、 size of cave、fracture interporosity flow coefficient、storage properties ratio.(8) The numerical calculating method of investigation radius was established, and part impermeable zone、part composite zone、nearby cave influence on investigation radius of carbonate reservoir at different moment.(9) The numerical calculating method of abnormal point distance was established, and abnormal point distance of carbonate reservoir with part impermeable zone、part composite zone、nearby cave was given.(10)10well layers were interpreted by using established fracture cave type carbonate reservoir well testing theory.This paper established mathematics model of fracture-cave type carbonate reservoir by BEM method, derived fracture-cave type reservoir medium type distinguishing method, calculated the investigation radius and abnormal point distance, provided theory guidance for solving fracture-cave type carbonate reservoir technical problems such as seepage mechanics in fracture-cave、numerical simulation technique and development mode、limit productivity、well pattern and spacing and so on, and open up the range of BEM application in oil and gas seepage flow. |
PDF Full Text Request