Horizontal Well Development Technology In Y Layered Sandstone Gas Field Policy Optimization Research

The Y gas field is a multi-layer monolithic sandstone gas field developed by horizontal wells.As of May 2020,145 gas wells have been put into production.The gas field has a short production time,and there are problems in the development process,such as the unclear relationship between gas and water,the unclear understanding of the production dynamic law of gas wells,the unreasonable production allocation of some wells,and the unclear law of water intrusion in gas wells.In this thesis,the geological characteristics of the target gas field are analyzed,the production decline analysis of gas wells is carried out by the Arps method and the modern production decline method,and the dynamic reserves of 145 gas wells are calculated by the flow material balance method and the Blasingame method.The dynamic reserves of the gas wells in the lower layer of the Y gas field are small.The Y gas field formation water discrimination chart was made,and the water production category of gas wells was determined.The critical liquid-carrying capacity of high-yield water and gas wells is calculated.According to the test data,the binomial and exponential productivity equations of 61 horizontal wells and 137 vertical wells were established,the unblocked flow rate of gas wells was determined,and the productivity of gas wells was evaluated.Six indicators of permeability,gas layer thickness,length of horizontal section,stable gas production,gas production index,and gas production per unit differential pressure were selected,and the nine-scale method of AHP was used to classify gas wells into three categories.Type I and II gas wells account for a high proportion and are mainly distributed in the middle and upper part of the gas field.The gas wells have large gas production rate,gas production index,and gas production per unit pressure difference.Five classification indicators including gas reservoir area,gas layer thickness,porosity,permeability,and gas saturation were selected,and the gas reservoirs were divided into three categories by the AHP nine-scale method and systematic clustering method.Type I gas reservoirs are mainly distributed in the upper part of the gas field,with large area and good porosity and permeability properties;Type III gas reservoirs are distributed in the lower part of the gas field with poor porosity and permeability properties.The abandoned pressure of the gas field is calculated by the burial depth method to be 2.76 MPa,and the recovery rate of the gas field is estimated to be 75%by the empirical method.Through empirical method,analogy method and numerical simulation method,the gas production rate,reasonable production pressure difference and reasonable production allocation of different types of gas reservoirs are determined.The reasonable production pressure difference of Class I gas reservoirs is 0.04～0.5 MPa,the production allocation is 60～90×10~4 m~3/d,and the gas production rate is 4.0%;the production pressure difference of Class II gas reservoirs is 0.3～1.25 MPa,the production allocation is 45-65×10~4 m~3/d,and the reasonable gas recovery rate of the gas reservoirs is 3.5%;the production pressure difference of the Class III gas reservoir is 0.6～2.0 MPa,and the production allocation is 30～50×10~4 m~3/d,and the reasonable gas recovery rate is 3.0%.