Study On Water Invasion Dynamic Law Of The SS14 Bottom Water Gas Reservior With Fractured Volcanic Rock

The formation water in water drive gas reservoir has both good and bad effects on the development of gas reservoir.Proper formation water entering the production zone can supplement the lost formation energy in the process of gas reservoir development.Excessive formation water influx will occur to seal gas reservoir reserves and increase the abandoned formation pressure of gas reservoir,resulting in the reduction of the ultimate recovery factor of gas reservoir.Because of the particularity and complexity of the reservoir rocks,the SS14 bottom water gas reservoir with fractured volcanic rock studied in this paper is quite different from the conventional gas reservoir in development.Therefore,it is of great practical significance for the development of volcanic gas reservoir to recognize its water invasion dynamic law.On the basis of a large number of literature research,the water invasion dynamic law of SS14 gas reservoir is studied as follows:(1)The geological and development characteristics of volcanic reservoir in SS14 gas reservoir are analyzed,and the development dynamic law of volcanic reservoir is deeply understood;(2)The types and water production sources of fractured volcanic gas reservoirs are studied.The four water invasion modes and water-sealed gas mechanism of blocking,detour flowing,dead pore and shut-in re-pressure of fractured gas reservoirs are identified.The influence of water invasion on gas reservoir development and the main factors affecting water invasion are analyzed;(3)The methods of water invasion identification,water influx calculation and water evaluation for bottom water gas reservoirs are systematically analyzed.According to the characteristics of the SS14 bottom water gas reservoir with fractured volcanic rock,a new method for calculating water influx considering the volume of water-sealed gas is proposed;(4)According to the space point sink theory,the physical model of formation water coning in bottom water gas reservoir is established,and the mathematical model of water particle movement is established on the basis of it.Considering the reservoir characteristics of volcanic gas reservoirs,the calculation models of formation water breakthrough time under single factors of stress sensitivity effect,slip effect,start-up pressure gradient and skin effect are established respectively.The strong brittleness of volcanic rocks makes it easy to fragment and form structural fractures,which leads to the development of fracture network in volcanic gas reservoirs.Therefore,fractal fracture permeability model is established based on fractal geometry theory to study the effect of fracture tortuosity on water breakthrough time of fractured volcanic gas reservoirs;(5)The dynamic control reserves of 26 gas wells in SS14 gas reservoir are calculated by case study.Three gas wells with water invasion were identified by dynamic production data,and water invasion of these three gas wells was calculated by production indication curve,apparent geological reserves and improved material balance method respectively.Comparing the calculation results of the three methods,the applicability of the improved material balance method in SS14 gas reservoir is verified.By using the improved material balance method and pressure drop method,the single well dynamic control reserves are calculated,and the influence of water invasion on the single well dynamic control reserves is analyzed;(6)The data of three wells in SS14 gas reservoir that have water invasion are substituted into the water breakthrough time model of bottom water gas reservoir under single factor condition,and the relationship between single factor condition and water breakthrough time is obtained.The influence rule of each single factor condition on water breakthrough time of gas well is analyzed and summarized.