本文選題：煤層氣 + 吸附氣解吸　； 參考：《煤炭學(xué)報》2017年12期

【摘要】：主要考慮了煤層氣開發(fā)過程中吸附氣非穩(wěn)態(tài)解吸的關(guān)鍵因素作用,建立了考慮吸附氣非穩(wěn)態(tài)解吸的煤層氣直井的線性滲流模型,并通過全隱式有限差分方法求得了內(nèi)邊界定流量、外邊界封閉滲流模型的數(shù)值解。通過數(shù)值結(jié)果分析主要表明了非穩(wěn)態(tài)解吸系數(shù)會使得無因次瞬時井底壓力與壓力導(dǎo)數(shù)的雙對數(shù)特征曲線在封閉邊界控制的擬穩(wěn)態(tài)流動段均出現(xiàn)下落趨勢,兩曲線間距離變寬,不再急劇上翹收斂為一條直線;這是由于吸附氣解吸能及時補(bǔ)充到氣藏,減緩了地層壓力的降落;而井筒儲集系數(shù)不影響由封閉邊界控制、受吸附氣解吸作用影響的擬穩(wěn)態(tài)流動段;表皮因子影響擬穩(wěn)態(tài)流動段無因次井底壓力的變化,但不影響擬穩(wěn)態(tài)流動段無因次井底壓力導(dǎo)數(shù)的變化。該線性滲流模型仍滿足Duhamel原理,生產(chǎn)數(shù)據(jù)分析時可利用反褶積技術(shù)手段,首先將按照擬壓力定義線性化的變流量生產(chǎn)數(shù)據(jù)轉(zhuǎn)化為單位流量下瞬時井底擬壓力數(shù)據(jù),然后基于所建滲流模型的數(shù)值解以及主要參數(shù)的敏感性影響分析結(jié)果,通過瞬時井底壓力特征曲線擬合方法對反褶積處理后的歸一化生產(chǎn)數(shù)據(jù)進(jìn)行分析,可解釋出表征煤層吸附氣解吸能力的非穩(wěn)態(tài)解吸系數(shù)、煤層滲透率、表皮因子、外邊界半徑等重要參數(shù)。由此建立了煤層氣直井生產(chǎn)數(shù)據(jù)的特征曲線系統(tǒng)分析方法。最后,通過一口煤層氣直井的實際生產(chǎn)數(shù)據(jù)分析驗證了所提出的煤層氣直井生產(chǎn)數(shù)據(jù)特征曲線分析方法的有效性和實用性;并采用解釋參數(shù)數(shù)據(jù)進(jìn)行模型計算,分析了吸附氣解吸作用對煤層氣井流量貢獻(xiàn)的瞬時變化規(guī)律;還通過公式推導(dǎo)表明了當(dāng)煤層中滲流到達(dá)穩(wěn)態(tài)時,整個煤層吸附氣解吸速度將等于煤層氣井生產(chǎn)的流量。
[Abstract]:In this paper, the key factors of unsteady desorption of adsorbed gas during the development of coalbed methane are considered, and the linear seepage model of straight well with unsteady desorption of adsorbed gas is established.The numerical solution of the internal boundary defined flow model and the outer boundary closed seepage model is obtained by using the fully implicit finite difference method.The numerical results show that the unsteady desorption coefficient can make the logarithmic characteristic curves of dimensionless instantaneous bottom pressure and pressure derivatives fall in the quasi-steady flow section controlled by closed boundary, and the distance between the two curves becomes wider.This is because the adsorption gas desorption energy is replenished to the gas reservoir in time, which slows down the fall of formation pressure, and the wellbore reservoir coefficient does not affect the control by the closed boundary.The pseudo-steady-state flow section affected by adsorption gas desorption, the epidermal factor affects the change of dimensionless bottomhole pressure in the pseudo-steady flow section, but does not affect the variation of dimensionless bottom-hole pressure derivative in the pseudo-steady-state flow section.The linear seepage model still satisfies the Duhamel principle, and the deconvolution technique can be used to analyze the production data. Firstly, the variable flow production data linearized according to the quasi-pressure definition is transformed into instantaneous bottom-hole pressure data under unit flow.Then, based on the numerical solution of the established seepage model and the results of sensitivity analysis of the main parameters, the normalized production data after deconvolution is analyzed by the fitting method of instantaneous bottomhole pressure characteristic curve.The unsteady desorption coefficient, coal seam permeability, skin factor, outer boundary radius and so on can be explained.Based on this, a systematic analysis method of characteristic curve for production data of coal bed methane (CBM) vertical well is established.Finally, the validity and practicability of the proposed method are verified by analyzing the actual production data of a coal bed methane vertical well, and the model calculation is carried out by using the interpretation parameter data.The instantaneous variation law of adsorption gas desorption to the flow rate of coalbed methane well is analyzed, and the formula derivation shows that the desorption rate of the whole coal bed adsorbed gas will be equal to the flow rate of coal bed methane well when the seepage in coal bed reaches steady state.
【作者單位】： 北京科技大學(xué)土木與資源工程學(xué)院;中國科學(xué)院力學(xué)研究所;
【基金】：國家自然科學(xué)基金資助項目(51404232) 中國博士后基金資助項目(2014M561074) 國家科技重大專項資助項目(2011ZX05046-03)
【分類號】：TD84

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