Laboratory Experiment And Numerical Simulation Of Natural Gas Drive In Low Permeability Reservoirs In Block P

Increasing the recovery factor of low permeability reservoirs is one of the main objectives of crude oil development in China at present.Low permeability reservoirs generally have the characteristics of low recovery factor using natural energy and ineffective water injection development.As the primary material in the oil layer,natural gas has the advantages of non-polluting the reservoir,being able to be recycled and effectively replenishing the formation energy.Using natural gas to develop reservoirs is one of the effective means to improve the recovery efficiency of low permeability reservoirs.The study area belongs to a low porosity and special permeability reservoir.The distribution of sand bodies in the reservoir has the characteristics of relatively scattered in the longitudinal direction and poor continuity in the plane,and the channel sand bodies change rapidly,the scale is small,the water injection development is ineffective,the single well production is low,and the effective development is difficult.After fully understanding the geological characteristics and fluid properties of the reservoir in the study area and conducting extensive research on domestic and foreign references,this article conducts indoor physical simulation experiments and reservoir numerical simulation research based on the actual situation of the study area.Among them,indoor experiments are divided into natural gas drive slim tube experiments and long core drive experiments.The slim tube experiment mainly determines the contact state between natural gas and crude oil underground,while the long core drive experiment mainly studies the degree of increase in natural gas drive oil efficiency compared to water drive and the appropriate natural gas drive method;The research on numerical simulation of oil reservoirs is divided into three major steps.The first step is to establish a geological model,the second step is to study the influencing factors of oil recovery rate in the study area,and the third step is to use numerical simulation software to optimize the parameters of natural gas injection engineering and predict the oil recovery rate for 15 years based on all research results.Through natural gas drive oil thin tube experiments,it was found that the crude oil in the study area cannot be mixed with natural gas within the range of formation fracture pressure.In the long core displacement experiment,it was determined that the water drive oil displacement efficiency in the study area was 27.13%,and the natural gas drive oil displacement efficiency was 35.00%.It is completely feasible to carry out natural gas drive in the study area;After comparing the methods of continuous gas drive and natural gas water alternating drive,it was determined that the research area should adopt the development method of gas water alternating drive,which is gas injection followed by water injection.Moreover,when the gas water slug size ratio is 1:2,the oil displacement efficiency is the highest,at 48.45%,which is 21.32percentage points higher than water drive oil displacement efficiency and 13.45 percentage points higher than continuous gas drive oil displacement efficiency.In a comprehensive indoor physical simulation experiment,numerical simulation research was conducted.It was found that under the geological conditions of the study area,the recovery rate was the highest when the permeability was 2×10^-3μm².The recovery rate decreased with the increase of formation porosity and effective thickness,and increased first and then decreased with the increase of gas injection intensity and well spacing.The recovery rate of the reverse nine point method well network was significantly higher than that of the five point method well network;After combining all the research results,it was determined that the study area would adopt natural gas drive development,using gas water alternating drive development,first injecting gas and then injecting water,using an irregular reverse nine point well network,with an average well spacing of about 290m,a gas injection rate of 12000 m3/d,and a gas water alternating cycle of1:1（month:month）.Numerical simulation methods were used to predict a 15 year oil recovery rate of 21.73%in the study area.Through the parameters designed in this article,the recovery rate of the research area has been significantly improved,providing a theoretical basis for the formulation of on-site development plans.