Water-drive Gas Percolation Mechanism And Simulation Theories And Methods

From the research of water-gas two-phase flow experiment, in the base of microscopic and macroscopic mechanism of water invasion in water drive gas reservoir, fractured water breakthrough gas reservoir model and its dynamic prediction theory and methods, gas well water out and well bore liquid loading rules, this paper studied water invasion rules and reasonable production scale for Leisan gas reservoir in Zhongba gas field. Main achievements are as follows.(1) Through many experiments, such as laser corrasion visualizing the water driving gas process with water-gas two-phase artificial physical model, water invasion process and encapsulated gas forming mechanism were studied for water drive gas reservoir. Combining with the researches of geologic characteristic of water drive gas reservoirs, water invasion characteristic and exploitation characteristic, pointed out that water breakthrough in fracture is the main reason of water invasion activity in gas reservoirs and that formation water flowed into gas reservoirs along fractures occupied gas flow access is the main reason affecting gas reservoir recovery, which resulted to gas produced difficultly in died gas zone of gas reservoir. At the same time, the water-gas distribution of plane radial flow and the influence of fracture on were studied.(2) The water encapsulating gas observed from the microscopic flow experiment and the phenomenon of existing start-up pressure were described mathematically. And the fluid breakthrough along big fracture was described with high-speed non-linear flow theory. Thus, the mathematic model and simulation theory and methods were established for gas and water flowing in complex media, such as cracks, fractures and big fractures, with which the performance of water invasion gas reservoir was simulated successfully. Therefore, this paper solved the quantitative dynamic simulation of water invasion gas reservoir from theories and methods.(3) The calculation methods of water-gas two-phase bore flow were brought forward on water and gas unsteady-state flow for water out of gas well. At the same time, the water and gas space and pressure distribution in well bore were calculated on water and gas unsteady-state flow. The relationship of water production rate in bottom hole with time was obtained. Thus, the research theory and method was established of water out rules in gas well.(4) For well bore liquid loading, the identifying method was put forward and the calculating method was studied of gas condensate loading in gas well. And the gas condensate loading was analyzed through nature gas water capacity, which has not reported in literatures. At same time, the equation of liquid column volume variation rules was put forward in gas well bore. Thus, the theory foundation was provided for the selection of reasonable gas wellproduction with water withdrawal.(5) On the guiding of experimental and theory achievement and the base of geologic characteristic and production characteristic of gas reservoir, the water invasion was studied for Leisan gas reservoir in Zhongba gas field. The main acquaintances were achieved. The water yield came mainly from the edge water in the west and south sides of gas reservoir. The water invasion ways was the uniform impellent from outer to inner and from underside to upside as a whole and the water breakthrough along fractures in local area. The edge water has entered gas zone in transverse orientation and impel non-uniformly on the affect of development status of local fracture and production rate of single well. Therefore, the controlling gas with water withdrawal could be carried out to improve the development effect for this gas reservoir. At the same time, the reasonable production scale was determined from the simulation study.From the above researches, this paper provided the guidance of theory and method for the reasonable development and the establishment of adjusting project of the fracture-pore edge water gas reservoir.