基于相渗滞后效应的水驱裂缝性气藏注N2提高天然气采收率机理  

Mechanisms of N2 injection in water drive fractured gas reservoirs to enhance gas recovery based on the phase permeability hysteresis effect

作　　者：王军磊[1] 位云生[1] 曹正林[1] 陈东[2] 唐海发[1] WANG Junlei;WEI Yunsheng;CAO Zhenglin;CHEN Dong;TANG Haifa(PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;PetroChina Tarim Oilfield Company,Korla,Xinjiang 841000,China)

机构地区：[1]中国石油勘探开发研究院 [2]中国石油塔里木油田公司

出　　处：《天然气工业》2025年第3期96-111,共16页Natural Gas Industry

基　　金：中国石油天然气股份有限公司基础性前瞻性项目“气藏采收率标定方法与复杂气藏提高采收率新技术研究”(编号:2024DJ86)。

摘　　要：裂缝与基质的渗透率级差导致水驱裂缝性气藏非均匀水侵严重,水淹区内以水封气和水锁气等形式存在的剩余天然气难以动用,严重影响了气藏天然气采收率的提高。为此,基于Killough、Carlson和Larsen经典相渗滞后理论,建立了先渗吸后驱替的气水相渗滞后模型,然后应用数值模拟方法,根据典型数据建立了一维长岩心模型和二维岩板模型,模拟了水锁气和水封气形成及解封过程并分析滞后作用对水侵和注气开发效果的影响,最后结合嵌入式离散裂缝技术建立了水驱裂缝性气藏注采概念模型,系统论证了注N2气提高天然气采收率的多重机理。研究结果表明:(1)气藏水侵后水淹区内的剩余天然气主要以2种形式存在,即气水两相中的水锁气以及被连续水相封隔的水封气;(2)在相渗滞后作用下,水锁气饱和度为渗吸残余气饱和度,高于驱替实验中的相渗端点饱和度值,导致水淹区内形成更多的水锁气;(3)裂缝与基质渗透率级差越高、缝网越发育、压力差越小的区域越易形成水封气,水锁气是形成水封气的直接原因;(4)注气以补能、挡水、驱替和置换4种方式重构了气藏压力场和饱和度场,通过重新动用未水淹区内剩余天然气提高了压力衰竭效率,通过重新驱替水淹区内水锁气和水封气提高了波及系数,进而提高了天然气采收率。结论认为,该研究成果为认识水侵过程中水封气和水锁气的形成机理、确定注气解封锁的最优技术政策,提供了理论依据,有助于含水裂缝性气藏的规模效益开发。The permeability contrast between fracture and matrix results in serious heterogeneous water invasion in water drive fractured gas reservoirs,and consequently the remaining natural gas in the form of water sealed gas and water locked gas in water flooded zones can be hardly produced,which seriously impacts the improvement of natural gas recovery factor.Based on Killough,Carlson and Larsen classical theories of relative permeability hysteresis,this paper establishes a gas-water relative permeability hysteresis model of imbibition first and then displacement.Then,based on typical data,the one-dimensional long core model and the two-dimensional rock plate model are established by means of numerical simulation,to simulate the formation and release process of water locked gas and water sealed gas.In addition,the influence of hysteresis on water invasion and water flooding development effect is analyzed.Finally,the concept model of injection and production in water drive fractured gas reservoirs is established on the basis of embedded discrete fracture model(EDFM),and multiple mechanisms of enhanced gas recovery by N2 injection are demonstrated systematically.The following results are obtained.First,the remaining gas in the water flooded zones after water invasion in gas reservoirs exists mainly in two forms,i.e.,water locked gas in gas and water phases,and water sealed gas isolated by continuous water phase.Second,under the action of relative permeability hysteresis,water locked gas saturation is imbibition residual gas saturation,which is higher than the saturation value at the end point of relative permeability in the displacement experiment,resulting in more water locked gas in water flooded zones.Third,water sealed gas tends to be formed in the zones with high permeability contrast between fracture and matrix,developed fracture network and small pressure difference,and water locked gas is the direct reason of water sealed gas formation.Fourth,gas injection reconstructs pressure field and saturation field in gas re

关 键 词：裂缝性气藏 水侵 水封 水锁 相渗滞后 注N2 天然气采收率 机理 

分 类 号：TE37[石油与天然气工程—油气田开发工程]