Reasearch On The Technology And Economic Boundary Of Horizontal Well In Low Permeability Gas Reservoir

Horizontal wells have found an increasingly wide utilization in the development of low permeability gas reservoirs.The indexes of horizontal section lengyth,production,production time,controlled reserve for an individual well,and the indexes of well spacing density,drainage area,well number,well spacing for a well network,etc.are the important technical indexes of horizontal wells during the development of gas reservoirs.How to scientifically,reasonably and economically determine these indexes' values is one of the important topics to develop low permeability gas reservoirs with horizontal wells.At present these technical indexes are mainly studied from the perspective of technology by using reservoir geology,seepage flow mechanics,gas reservoir engineering theory.However,no really systematic studies have been conducted in terms of technical and economic coupling.This dissertation was based on the theory and methods of seepage mechanics,fluid mechanics,gas reservoir engineering,and technical economics.Methods of inductive-deduction,systematic analysis,combination of theoretical research and empirical analysis,etc.were employed,and the quatenity of concept-theory-method-empirical study and mutually reinforcing technological approach were adopted.A evaluation model of technical and economic limits for low permeability gas reservoirs development with an individual horizontal well or well pattern was established systematically,and the corresponding research on technical and economic limits were carried out,around the following four issues about low permeability gas reservoir development with horizontal wells:the meaning of technical limits and economic limits;the evaluation model of technical limits,the evaluation model of economic limits,and the influence parameters analysis.The following results can be summarized:(1)Learning from the oil and gas field development engineering and principles of technical economics,technology limits and economy limits were defined for the indexes of individual well or well network in low permeability gas reservoir development with horizontal wells.The meaning and characteristics of each index were analyzed,thus a system of main technical and economic indexes for low penneability gas reservoirs development with individual horizontal well or well network was established.(2)Based on the theory and methods of seepage mechanics,fluid mechanics,gas reservoir engineering,the technical limits evaluation model of the relationship between horizontal section length and well production or bottom-hole pressure,and the technical limits evaluation model of horizontal well production,reserve,well spacing density,etc.main technical indexes were established for low permeability gas reservoirs development with individual horizontal well or well network.These evaluation models can not only laid the foundation for the technical design of horizontal wells in low penrmeability gas reservoir development,but also provide a technical basis for the economic limits evaluation modes of horizontal section length,production,production time,controlled reserve of an individual horizontal well and well spacing density,drainage area,well number,well spacing of a horizontal well network.(3)Based on the technical limits evaluation model of the main technical indexes of the individual horizontal well and well network,an evaluation model of economic limits of horizontal section length during the low permeability gas reservoirs development with an individual horizontal well was established employing dynamic break-even analysis and marginal analysis.Based on this model,the evaluation models of economic limits were further proposed for production,production time,controlled reserve of an individual horizontal well and well spacing density,drainage area,well number,well spacing of a horizontal well network.And the corresponding calculation method was given to provide theoretical and method support for the technical and economic evaluation of horizontal well development in low permeability gas reservoirs.(4)In terms of the economic limits evaluation models of individual horizontal well or well network,the curve charts of the relationships of horizontal well section or economic production time and net present value of horizontal well production,economic production,economic controlled reserve,economic well spacing density,economic drainage area,economic well number,and economic well spacing of horizontal wells respectively,were calculated and plotted.Employing these charts the main technical indexes economic limits of individual horizontal well and well network were determined.The influence of production parameters,gas reservoir parameters,horizontal well parameters and economic parameters on the economic limits of the main technical indexes of horizontal wells were discussed applying sensitivity analysis method.And the categories of influencing factors were given respectively to point out the direction for the monitoring and controlling of the horizontal well development in low permeability gas reservoirs.(5)Based on the technical and economic limits evaluation models of horizontal section length,production and controlled reserve in the low permeability gas reservoirs development with horizontal wells,the case of LP horizontal well in JB low permeability gas reservoir are studied empirically.The technical and economic limits of horizontal section length,production and controlled reserve of LP in JB were calculated based the foundation data of corresponding evaluation parameters.By the comparative analysis,the results showed that the calculation method of the technical and economic limits presented in this paper is feasible,functional and practical.This dissertation combined the gas reservoir engineering method with the technical economics theory,and carried out the research aiming at the four issues that must be solved in the study of technical and economic limits of low permeability gas reservoirs development with horizontal wells.The innovation points of this dissertation are outlined as follows:(1)The definition of economic limit in the low permeability gas reservoirs development with horizontal wells was proposed from the horizontal section length,production,production time,controlled reserve,etc.eight aspects.And the indexes system of economic limits was established relatively.(2)The calculation models of low permeability gas reservoirs development with horizontal wells were established more comprehensively and deeply,which indicated the relationships between economic limits indexes and production parameters,gas reservoir parameters,horizontal well parameters,natural gas property parameters and economic parameters.(3)The sensitivity to influencing factors of economic limits in the low permeability gas reservoirs development with horizontal wells studied comprehensively.