Research On Description Technology Of Complex Carbonate Reservoirs In R Gas Field

The geological situation of carbonate rock reservoir in R Gas Field is complicated,which has a strong reservoir heterogeneity,it is difficult to accurately identify the reservoir type.In order to resolve the issue of reservoir description and make a support to reasonably and efficiently develop the field,some embedded studies on well test interpretation and production dynamic curve analysis are systematically carried out in the complex carbonate reservoir of R Gas Field.Based on thoroughly grasping the characteristic of geology and physical property,the analytical well test method is used to respectively interpret the typical reservoir of R Gas Field.For some cases,such as serious reservoir heterogeneity,cracks and complex boundaries which are hardly settled by analytical well test methods,the numerical method is applied to establish and interpret the relevant reservoir model.Meanwhile,the application of gas productivity index per reservoir thickness in discerning reservoir type has been explored and validated.Following main works are completed.(1)Based on testing documents,the reservoir pressure,temperature and fluid component concentration of the 27 wells in main fields are counted,and the gas reservoir is assorted according to the census results and clascification criteria.There is a quantitative assessment on porosity and permeability data of 500 cores in R Gas Field,the result indicates that the average value of porosity and permeability respectively is 9.52%and 0.56mD,the physical property of R Gas field is proved to be not good,the reservoir is a fracture-pore type.(2)72 well test interpretation materials of the R Gas Field are counted,all of them are classified to five basic types:homogeneous reservoir,dual-media reservoir,composite reservoir,fractured reservoir and complex boundary reservoir.Based on the theoretical chart of well test,the log-log curve of the typical well in different reservoirs has been interpreted.The sensitivity analysis of characteristic parameters in dual porosity reservoir is also accomplished.The deliverability of 20 horizontal wells in the major reservoir is analyzed,and there is an in-depth analysis in the log-log curve and the effect factor of its tracing pattern.At last,the principal problem and some proposals to deal with these issues of the analytical well test in R Gas Field have been presented.(3)Considering the disadvantage of the analytical method in discerning complex reservoirs,the geometric and numerical model of different reservoir types,such as homogeneous reservoir,radial composite reservoir,complex boundary reservoir,fractured reservoir in vertical and horizontal wells,are established on the basis of static data and analytical well test interpretation.Meanwhile,tow different methods are used to simulate fracture morphology in the reservoir and the effect which the flow conductivity of fissures in horizontal well has on its log-log curve is particularly analyzed.At last,the numerical well test is applied to deal with the boundary problem of a productive well.The application effect shows that the numerical well testing technology has obvious advantages in resolving the ambiguity of reservoir characteristics due to the limitation of the test time and dealing with the complex reservoir situation,which can be perfectly applied to the description of reservoir characteristics.(4)A large number of production and pressure data under the condition of different work systems have been thoroughly studied,the result shows that the dynamic parameter during the flow period actually contains a large amount of information about the variation of reservoir physical property.An implicit linear relationship between the reciprocal gas productivity index per reservoir thickness and the time log is derived from the transient pressure drop equation of gas well,which plays an auxiliary role in discerning reservoir types.The method is verified by numerical simulation and actual test data.These dynamic methods of complex carbonate reservoir description mentioned above are absolutely based on actual reservoir situation and verified by the field data.The result shows that these methods are able to solve issues in discerning reservoir type of R Gas Field.