Study On The Decrease Type And Capacity Of Horizontal Wells In The Low Pressure And Tight Gas Reservoirs Of MJ Gas Field

With the steady decline in conventional oil and gas resources and the global increasing demand for oil and gas, the importance of unconventional oil and gas resources, a considerable proportion of which is tight sandstone gas, have become increasingly prominent. As we all know, low permeability and tight gas reservoirs have low porosity and permeability, poor connectivity, and there is start-up pressure for most of this type of reservoir, making it difficult to develop. How to efficiently develop such gas reservoir is a problem needed to be solved. Currently fractured horizontal well technology is a hot tool for the development of low permeability and tight gas reservoirs. But there is a significant production decline for some fractured horizontal wells during development of low permeability and tight gas reservoirs. Therefore, the research on the production capacity of fractured horizontal wells is needed to carry out urgently.Using gas reservoir dynamic analysis, gas reservoir engineering and the numerical simulation methods, combined with static geological data of MJ gas field JP2gas reservoir, a typical low permeability and tight gas reservoir, the research about production decline law and production capacity of fractured horizontal wells in low permeability and tight gas reservoir is carried out.Firstly, geological characteristics, development characteristics and the current main problems, for the MJ gas field JP2gas reservoir, are analyzed.Then with the dynamic production data of15fractured horizontal wells in MJ gas field JP2gas reservoir, using the modern oil and gas well production decline analysis methods, gas well controlled reserves, frustrated radius, decreasing type, decline rate and other parameters are calculated by a variety of production decline analysis methods. Then the reason for production decline of fractured horizontal well in JP2gas reservoir is analyzed and development countermeasures are studied.Then based on the start-up pressure in low permeability and tight gas reservoir, fractured horizontal well productivity formula is set up under the consideration of start-up pressure gradient. With the static parameters of fractured horizontal wells in JP2gas reservoir, sensitivity analysis of factors-horizontal well length, start-up pressure gradient, pressure fracture number, and fracture half length-affecting horizontal well production capacity is conducted.Then according to the real fine geological model of JP2gas reservoir, the mechanism model of the effect to fractured horizontal well productivity is set up. By numerical simulation methods, the influence of start-up pressure gradient on fractured horizontal well productivity is analyzed. Then it is implemented to study the affecting law of parameters, such as the position of horizontal well in vertical, horizontal well length, and fracture spacing, fracture number, and fracture half length, and fracture diverting capacity, on fractured horizontal well productivity. Lastly the fractured horizontal well parameters and fracture parameters combination are optimized. The main results of this research are:(1)the production of15fractured horizontal wells in MJ gas field JP2gas reservoir decline hardly, and the average rate is about53.99%, the average gas well controlled reserves is0.1825X108m3, the average frustrated radius is145.37m;(2)the establishment of a fractured horizontal well productivity model under consideration of starting pressure gradient, capacity factors sensitivity analysis shows the effect of starting pressure gradient of fractured horizontal well production "can not be ignored", the biggest gas production can lead to reduced56.69%;(3)JP2gas reservoir fine numerical simulation indicated that the maximum pressure gradient can result in lower gas yield21.12%, while the pressure crack can effectively reduce the influence of starting pressure gradient of gas production;(4)horizontal well drilling site selection high in favor of gas well stimulation, and the horizontal length of the well and the pressure crack spacing, number, half-length, increasing the conductivity, and can increase gas production to varying degrees, but the growth rate decreases.