雙孔介質頁巖氣藏產能遞減曲線動態分析

孔凡就 韓建國 何永輝 苗冀清

【摘要】頁巖氣藏里的孔隙結構復雜，微孔隙普遍發育，主要儲集類型可分為：裂縫和孔隙。在開采過程中，吸附在微孔隙內表面的吸附氣發生解吸作用，變成游離氣。在壓差的作用下進入裂縫系統，以層流形式流入井筒。根據頁巖氣滲流機理、吸附氣解吸特征和滲流理論建立雙孔介質頁巖氣藏數學模型，并對模型求解，分析了儲層模型、吸附氣、表皮系數、幾何因子等對氣井產能變化的影響。結果表明：開發初期，地層壓力差較小，吸附氣解吸量較少，對氣井產能影響很弱；開發后期，吸附氣的解吸量增加，保證了氣體的供應量，延長了氣井穩產時間。

【關鍵詞】頁巖氣；孔隙結構；吸附氣；數值模擬；產能預測

Performance Analysis on Production Decline Curves of Shale Gas Reservoir in Dual-porosity Media

Kong Fanjiu，Han Jianguo，He Yonghui，Miao Jiqing

（China Petroleum Pipeline Bureau Horizontal Directional Drilling Company， Langfang City， Hebei Province，065000）

[Abstract]As the pore structure of shale gas reservoir is complex， micropore is commonly developed， and reservoir type is mainly divided into cracks and pores. In the mining process， the adsorbed gas in the inner surface of micropore will be dissociated， then turned into free gas. Under the difference of pressure， free gas flows into fracture system， then into the wellbore as laminar flow. The mathematical model of dual porosity shale gas is established based on the shale gas percolation mechanism， the adsorbed gass desorptive characteristics and percolation theory.Then solve the model， make an analysis of the gas well productivity changes of double reservoir model， adsorbed gas， skin factor and geometrical factor and so on. The results show that in the early stage of development， the formation pressure difference is small， the amount of adsorbed gas desorption is less， and gas well productivity impact is weak； Later， the adsorbed gas desorption increased to ensure the supply of gas and extend a gas well stable time.

[Keywords]shale gas；pore structure；adsorbed gas；numerical simulation；production capacity forecast.

前言

頁巖氣是一種非常重要的能源，主要儲存在泥頁巖和高碳泥巖中。頁巖氣開發具有開采和生產周期長的優勢，大部分產氣頁巖分布范圍廣、厚度大，且普遍含氣，這使得頁巖氣井能夠長期穩定地產氣[1]。Daniel[2]對Appalachia盆地中的八塊泥盆系頁巖巖芯進行分析，得出在氣藏壓力條件下，巖芯孔隙度小于0.2%，滲透率小于0.1毫達西；代平[3]通過實驗研究，分析了低滲透儲層中有效應力對孔隙度和滲透率的影響；李治平[4]從微觀角度建立了滲透率動態數學模型，并分析了吸附氣和分子擴散流動對滲透率的影響；錢旭瑞[5]從地質角度分析了有機碳、有機質成熟度、礦物組成等對頁巖氣產能的影響；周登洪等[6]從地質和開發兩個方面綜述了頁巖氣井產能影響因素；……