Research into relative permeability dynamic calculation methods for coalbed methane reservoirs
HUANG Tianhao, WANG Zhiming, ZENG Quanshu, CAI Xianlu, DAI Anna
1 College of Petroleum Engineering, China University of Petroleum-Beijing, Beijing 102249, China 2 State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum-Beijing, Beijing 102249, China
摘要?
為獲取煤層氣藏氣水相對滲透率實際變化特征,，進一步深化對煤層氣藏氣水產(chǎn)出規(guī)律的認(rèn)知,，構(gòu)建了結(jié)合煤層氣藏實時動用情況的煤層氣藏相對滲透率動態(tài)計算方法,。該方法首先通過多煤層全過程耦合流動模型對目標(biāo)單煤層或多煤層進行產(chǎn)量歷史擬合,，獲得儲層和流體的基本物性參數(shù),。而后,，基于得到的基本物性參數(shù)開展煤層氣井全生產(chǎn)周期產(chǎn)能預(yù)測，同時,，根據(jù)儲層壓降漏斗的實時擴展規(guī)律對儲層參數(shù)進行平均化處理,，并結(jié)合流體的實際運移情況計算煤層氣藏氣—水相對滲透率曲線。研究結(jié)果表明：本文提出的煤層氣藏相對滲透率動態(tài)計算方法可在對煤層氣藏內(nèi)部動用情況實時定量分析的基礎(chǔ)上,，動態(tài)計算煤層氣藏實際氣水相對滲透率,。通過本文提出的方法計算得到的氣相相對滲透率曲線上存在反轉(zhuǎn)點，其反應(yīng)儲層中的解吸氣開始穩(wěn)定,、連續(xù)的供應(yīng),。若不考慮儲層壓降漏斗實際擴展規(guī)律，對儲層參數(shù)進行全域平均,，計算得到的煤層氣藏氣水相對滲透率將偏低,。對于多煤層氣藏，竄流效應(yīng)導(dǎo)致的層間流體質(zhì)量交換和儲層壓力下降不可忽略,，生產(chǎn)3 y 時氣相竄流量與產(chǎn)氣量比值可達0.57,，水相竄流量與產(chǎn)水量的比值可達0.69。忽略竄流量條件下計算得到的煤層氣藏氣水相對滲透率偏低,，僅為考慮竄流量條件下的42.89% 和24.40%,。在煤層氣井實際生產(chǎn)過程中，含水飽和度保持在較高值,，大于40%,，受高含水飽和度的制約，煤層氣藏氣相相對滲透率值較低,，小于0.2,。
In order to obtain the actual change characteristics of the gas-water relative permeability in coalbed methane (CBM) reservoirs and to further deepen the understanding of the gas-water production process of CBM reservoirs, a relative permeability dynamic calculation method of CBM reservoirs combined with the real-time production situation of the reservoir was constructed. Firstly, the production history match of the target single coal seam or multiple coal seams is carried out using the multiple coal seam whole process coupling flow model, which is to obtain the basic physical parameters of the reservoir and fluid. Then, based on the obtained basic physical parameters, the full production cycle productivity prediction of the CBM well is carried out. At the same time, the reservoir parameters are averaged according to the real-time expansion behavior of the reservoir pressure drop, and the gas-water permeability curve of the CBM reservoir is calculated based on the averaged reservoir parameters and the actual fluid migration. The results show that the relative permeability dynamic calculation method of CBM reservoirs proposed in this paper can dynamically calculate the actual gas-water relative permeability of the CBM reservoir on the basis of real-time quantitative analysis of the internal production situation of the CBM reservoir. There is a reversal point on the gas relative permeability curve calculated by the method proposed in this paper. The reversal point characterizes the stable and continuous supply of desorption gas in CBM reservoirs. If the actual expansion of the CBM reservoir pressure drop is not considered and the reservoir parameters are averaged in the whole area, the calculated gas-water relative permeability of the CBM reservoir will be low. For multiple coal seam reservoirs, the interlayer mass exchange of fluids and the decrease in the reservoir pressure caused by the crossflow cannot be ignored. The ratio of the crossflow of gas to gas production can reach 0.57, and the ratio of the crossflow of water to water production can reach 0.69 after 3 years of production. The calculated gas-water relative permeability of the CBM reservoir under the condition of ignoring the crossflow is low, which is only 42.9% and 24.4% respectively of the calculated gas-water relative permeability under the condition of considering the crossflow. In the actual production process of CBM wells, the water saturation remains at a high value, more than 40%. Restricted by the high water saturation, the gas relative permeability of CBM reservoirs is low, less than 0.2.
