Blasingame气井变产量拟稳态压降方程存在的问题及其推导与应用  

Existing problems of Blasingame's pseudo-steady-state pressure drawdown equation with variable rate for gas wells along with derivation and application

作　　者：陈元千[1] 王鑫[1] 刘洋[1] CHEN Yuanqian;WANG Xin;LIU Yang(Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China)

机构地区：[1]中国石油勘探开发研究院,北京100083

出　　处：《中国海上油气》2023年第6期70-77,共8页China Offshore Oil and Gas

摘　　要：稳定产量的压降曲线拟稳态法,又称为弹性二相法,可用于评价断块、岩性和裂缝系统等封闭气藏的原始地质储量,因此受到广泛的重视和应用。尤其是Blasingame提出的气井变产量拟稳态方程,受到国内外业内人士的普遍重视。本文基于达西基础单位,对变产量的拟稳态方程进行了推导和单位变换,表明了Blasingame变产量拟稳态方程存在的问题。对于低渗气藏来说,在进行井底压降曲线测试时,气井的产量难以保持稳定,而会随时间缓慢下降,因此形成了井底流压和产量同时下降的状态。对此,本文提出了双变函数的概念,并表示为J(t)=Δp(t)/qg(t)。基于双变函数提出了确定气井控制原始地质储量(OGIP)、有效渗透率和递减率的解析法和典型曲线拟合法。通过实例应用表明,两种方法评价的OGIP、有效渗透率和递减率基本一致。但解析法简单、实用、可靠,而典型曲线拟合法较为繁琐,并存在人为拟合影响的多解性。The pseudo-steady state method of pressure drawdown curve for stable rate,also known as elastic two phase method,which can be used to evaluate the original gas in place of closed gas reservoirs such as fault block reservoirs,lithological reservoirs and fractured systems.Therefore,it has received widespread attention and application.Especially,the pseudo-steady state equation with variable rate for gas wells proposed by Blasingame is widely valued by domestic and international industry professionals.Based on Darcy base units,the pseudo-steady state equation with variable rate is derived and the units are transformed in this paper,and problems existing in Blasingame's pseudo-steady state equation with variable rate have been proved.For low-permeability gas reservoirs,the production of gas wells is difficult to maintain stable during the bottomhole pressure drawdown curve test,but will decline slowly with time.Therefore,the state of simultaneous decline of the bottomhole flowing pressure and production is formed.In this paper,the concept of bivariate function is proposed and expressed as J(t)=Δp(t)/qg(t).Based on the bivariate function,the analytical method and type curve matching method for determining the well-controlled original gas in place(OGIP),effective permeability and decline rate are proposed.The example application shows that the OGIP,effective permeability and decline rate evaluated by the two methods are basically consistent.However,the analytical method is simple,practical and reliable,while the type curve matching method is complicated,and there are multiple solutions affected by artificial matching.

关 键 词：气井 变产量 Blasingame 压降曲线 方程 问题 双变函数 井控 原始地质储量 有效渗透率 递减率 

分 类 号：TE37[石油与天然气工程—油气田开发工程]