一種新型天然氣壓縮因子數(shù)值計(jì)算方法

1、 收稿日期:20100612;改回日期:20100919基金項(xiàng)目:國(guó)家重大專(zhuān)項(xiàng)“南海深水油氣勘探開(kāi)發(fā)示范工程”(2008ZX05056002研究成果作者簡(jiǎn)介:管虹翔(1980,男,工程師,2006年畢業(yè)于西南石油大學(xué)機(jī)電專(zhuān)業(yè),現(xiàn)從事油氣田開(kāi)發(fā)方面的生產(chǎn)科研工作。文章編號(hào):10066535(201102008504一種新型天然氣壓縮因子數(shù)值計(jì)算方法管虹翔1,段國(guó)喜2,齊桃1,李偉1,李偉超1(1.中海油研究總院,北京100027;2.中海油天津分公司,天津300452摘要:天然氣壓縮因子是天然氣重要的物性參數(shù)之一,傳統(tǒng)計(jì)算方法對(duì)于高壓天然氣的計(jì)算存在較大誤差。綜合利用傳統(tǒng)壓縮因子圖版與高壓天然氣

2、壓縮因子實(shí)驗(yàn)數(shù)據(jù)進(jìn)行擬合,得到了同時(shí)適用于中低壓及高壓范圍的天然氣壓縮因子計(jì)算公式。計(jì)算顯示在低壓段平均誤差為3.3%,在高壓段平均誤差為2.5%。將這一公式應(yīng)用于氣井壓力的計(jì)算中,取得了較高的計(jì)算精度。關(guān)鍵詞:壓縮因子;天然氣;常規(guī)氣井;高溫高壓氣井;計(jì)算方法中圖分類(lèi)號(hào):TE31文獻(xiàn)標(biāo)識(shí)碼:A引言目前使用較多的天然氣壓縮因子計(jì)算方法,包括Dranchk Abu Kassem 方法(DAK 12,Ha-nkinson Thomas Phillips 方法(HTP 3,Dran-chuk Purvis Robinson 方法(DPR 4,以及由石油大學(xué)李相方教授根據(jù)天然氣壓縮因子圖版擬合的李相方

3、方法(LXF 。這些計(jì)算公式均是根據(jù)Standing 和KatZ 1942年提出的壓縮因子圖版5采用不同擬合方法擬合得到的6。在不同的對(duì)比壓力及對(duì)比溫度下,誤差均較大。根據(jù)李相方教授的統(tǒng)計(jì),各方法的最大誤差均超過(guò)了55%7。近幾年國(guó)內(nèi)相繼發(fā)現(xiàn)了一批高溫高壓天然氣田8。原有壓縮因子計(jì)算方法適用壓力范圍低的弊端逐漸暴露。石油大學(xué)郭緒強(qiáng)教授針對(duì)這一問(wèn)題進(jìn)行了相關(guān)試驗(yàn),取得了豐富的高壓天然氣實(shí)驗(yàn)數(shù)據(jù)9。將郭緒強(qiáng)教授發(fā)表的高壓天然氣實(shí)驗(yàn)數(shù)據(jù)與傳統(tǒng)天然氣壓縮因子圖版10疊加,發(fā)現(xiàn)天然氣壓縮因子在高壓階段具有較強(qiáng)的延展性,表現(xiàn)出了較好的規(guī)律。利用三維繪圖軟件將數(shù)據(jù)進(jìn)行處理,可以發(fā)現(xiàn)天然氣壓縮因子曲面較為復(fù)雜

4、。因此,本文利用傳統(tǒng)壓縮因子圖版與郭緒強(qiáng)教授發(fā)表的高壓天然氣實(shí)驗(yàn)數(shù)據(jù)進(jìn)行擬合,嘗試找到高精度的能夠同時(shí)兼顧高中低壓范圍的壓縮因子計(jì)算方法。1公式擬合1.1分界線的確定天然氣壓縮因子具有較強(qiáng)的規(guī)律性。在低壓段,壓縮因子隨對(duì)比壓力的增大先降低后升高,在中高壓段,壓縮因子隨對(duì)比壓力的升高而增加。壓縮因子的變化規(guī)律決定了無(wú)法使用一種函數(shù)形式對(duì)其進(jìn)行統(tǒng)一的描述,因此嘗試使用分段的方法進(jìn)行描述。HTP 方法也使用了分段的方法進(jìn)行描述,但是其給出的分界線是一個(gè)定值(p pr =5。這一分界線較好的保證了高壓段的規(guī)律性,但是對(duì)于低壓段,其規(guī)律性仍舊難以保障。因此本文根據(jù)圖1中各曲線的拐點(diǎn)進(jìn)行分割,其分界如圖1

5、所示 。圖1天然氣壓縮因子分界曲線對(duì)分界曲線進(jìn)行數(shù)據(jù)回歸,分界線上壓縮因子86特種油氣藏第18卷Z與對(duì)比壓力ppr和對(duì)比溫度T pr的關(guān)系如下式所示:Z=0.1547Tpr 51.7476Tpr4+7.875Tpr317.835Tpr 2+20.573Tpr8.8579(1p pr =1.266674Tpr4+11.683417Tpr339.764243Tpr 2+59.021716Tpr28.657098(2式中:Z為天然氣壓縮因子;p pr為對(duì)比壓力,是實(shí)際壓力與絕對(duì)壓力的比值;T pr為對(duì)比溫度,是實(shí)際溫度與絕對(duì)溫度的比值。1.2目標(biāo)函數(shù)及系數(shù)的確定由天然氣壓縮因子圖版可以看出,當(dāng)溫度一

6、定時(shí),壓縮因子Z值與對(duì)比壓力p pr在低壓段呈曲線關(guān)系,在高壓段呈線性關(guān)系。通過(guò)計(jì)算對(duì)比,高壓段采用線性函數(shù),低壓段采用二次曲線函數(shù)作為目標(biāo)函數(shù)形式。Z低=a(Tprppr2+b(Tprppr+c(TprZ高=d(Tprppr+e(Tpr(3式中:a(T pr、b(T pr、c(T pr、d(T pr、e(T pr是關(guān)于T pr的函數(shù),為相關(guān)式的系數(shù)。對(duì)壓縮因子圖版數(shù)據(jù)和實(shí)驗(yàn)數(shù)據(jù)按照對(duì)比溫度T pr進(jìn)行分組,利用公式(3進(jìn)行回歸(表1、2。 第2期管虹翔等:一種新型天然氣壓縮因子數(shù)值計(jì)算方法87對(duì)表1及表2數(shù)據(jù)進(jìn)行擬合,可得到各系數(shù)與對(duì)比溫度T pr 的關(guān)系式。a (T pr =0.1736T

7、 pr 4+1.3481T pr 33.8363T pr 2+4.7201T pr 2.1017(4b (T pr =0.2154T pr 31.4096T pr 2+3.106T pr 2.3266(5c (T pr =0.0107T pr 3+0.0673T pr 20.1412T pr +1.0987(6d (T pr =0.0799ln (T pr +0.1016(7e (T pr =0.789ln (T pr +0.1276(8選取壓縮因子圖版和實(shí)驗(yàn)數(shù)據(jù)中對(duì)比溫度及對(duì)比壓力,利用公式(3計(jì)算壓縮因子。在低壓段平均誤差為3.3%,在高壓段平均誤差為2.5%,公式具有較高的精確度(表3。

8、 由表3可以看出,在對(duì)比溫度為1.05時(shí),本文計(jì)算方法與其他計(jì)算方法一樣誤差較大,最大誤差達(dá)到了60%。從壓縮因子三維圖可以看出,對(duì)比溫度在1.05 1.10之間時(shí),Z 值曲面表現(xiàn)出了較強(qiáng)的扭曲性,這也是造成各方法預(yù)測(cè)精度均較低的主要原因。因此,需要對(duì)對(duì)比溫度在1.05 1.10之間的數(shù)據(jù)重新進(jìn)行回歸,其系數(shù)關(guān)系式如下:a (T pr =4.076T pr 4.5034(9b (T pr =2.9681T pr +2.9204(10c (T pr =0.4617T pr +0.5033(11當(dāng)對(duì)比溫度在1.05 1.10之間時(shí),系數(shù)a (T pr 、b (T pr 、c (T pr 選擇式(9

9、 (11計(jì)算,當(dāng)對(duì)比溫度大于1.1時(shí),系數(shù)a (T pr 、b (T pr 、c (T pr 選擇式(4 (6計(jì)算。經(jīng)修正,壓縮因子計(jì)算精度大為提高,但其最大誤差仍有25%(表4。2適用條件及實(shí)例計(jì)算2.1適用性分析本文提出的計(jì)算方法(GHX ,同時(shí)適用于中 低壓與高壓的天然氣井計(jì)算,僅在對(duì)比溫度低于1.1時(shí)(為超低溫氣井精度較低,在其他對(duì)比溫度條件下,具有較高的精度,平均誤差為1.7%。對(duì)比目前常用的幾種天然氣壓縮因子計(jì)算方法,在典型對(duì)比溫度與壓力條件下,幾種方法計(jì)算誤差見(jiàn)表5。從表5可以看出,本文計(jì)算方法除在極個(gè)別條件下,均具有比較高的計(jì)算精度,具有較好的穩(wěn)定性,適用于常規(guī)天然氣井及高溫高

10、壓氣井。并且本文在擬合過(guò)程中考慮了郭緒強(qiáng)教授實(shí)驗(yàn)獲得的340個(gè)高壓天然氣壓縮因子數(shù)據(jù)(對(duì)比壓力最高達(dá)88特種油氣藏第18卷20.71,對(duì)高壓天然氣井計(jì)算也具有較好的代表性。 2.2實(shí)例計(jì)算某氣田射孔深度為3394m,測(cè)試日產(chǎn)氣為14.2104m3/d,井口壓力為40.9MPa,測(cè)試井底流壓為50.3MPa,屬異常高壓天然氣田。利用Pipesim軟件建模,從井口壓力反算求得井底流壓為49.23MPa,誤差為1.07MPa。分析認(rèn)為,軟件中使用的壓縮因子計(jì)算公式為一般壓力下的計(jì)算公式,對(duì)于高壓天然氣計(jì)算存在較大誤差,影響了計(jì)算的結(jié)果。利用本文求得的壓縮因子計(jì)算公式進(jìn)行計(jì)算,結(jié)合軟件計(jì)算的摩阻損失等

11、數(shù)據(jù),井底流壓為50.4MPa,誤差僅0.1MPa,精度遠(yuǎn)高于軟件中默認(rèn)的計(jì)算方法。說(shuō)明本文提出的壓縮因子計(jì)算公式具有較高的精確度。3結(jié)論本文根據(jù)壓縮因子圖版與收集到的高壓壓縮因子實(shí)驗(yàn)數(shù)據(jù),擬合出了同時(shí)適用于中低壓與高壓的天然氣壓縮因子計(jì)算公式,取得了精度較高的計(jì)算結(jié)果。但是同時(shí)也應(yīng)看到,在對(duì)比溫度較低時(shí)(1.05T pr1.10,本文方法以及其他計(jì)算方法均不能較好計(jì)算壓縮因子,因此在今后的工作中應(yīng)加強(qiáng)這一方面的研究。參考文獻(xiàn):1汪周華,等.酸性天然氣壓縮因子實(shí)用算法對(duì)比分析J.西南石油學(xué)院學(xué)報(bào),2004,26(1:4750.2Dranchuk P M,AbouKassem J H.Calcu

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14、.油層物理M.北京:石油工業(yè)出版社,2005:108.編輯孟凡勤and laboratory data by employing statistical analysis,empirical equation and relative permeabilitymercury penetration analysisThe type and composition of water production are determinedThe study result indicates that the distribution of gas and water dis-plays"gr

15、adual complementary"relationship,with relatively waterrich area in the northwest;the water produced from the forma-tion comprises condensate water,movable water and free water;formation water production can be controlled by controlling draw-down pressureThis study provides basis for management

16、of water production wells and selection of development zones in the gas fieldKey words:formation water;type of water production;distribution of gas and water;Sulige gas fieldPreliminary study on interwell communication and fracture development in theupper Shaximiao gas reservoir of the Xinchang gas

17、fieldWANG Xu,LI Zuyou,DENG Wenlong,YAN Xiaoyong,XU Guangpeng(Southwest OilGas Company,SINOPEC,Deyang,Sichuan618000,ChinaAbstract:Interwell communication is increasingly seen in the upper Shaximiao gas reservoir of the Xinchang gas field due to fractu-ring operationThis paper comprehensively analyzes

18、 earth stress,fracturing fracture monitoring,pressure drop in well block,time of interwell communication,and interwell azimuth relationship,generalizes that fracturing fracture development is the main reason for interwell communicationGas well fracturing can lead to sand production and plugging in a

19、djoining gas wellsOn this basis,three preventive measures of interwell fracturing communication are proposed:the orientation of earth stress and fracture development shall be fully considered when placing infill wells in a gas reservoir;the technology of perforation and fracturing shall be optimized

20、;and the adjoining wells shall be shut in to build up pressure when performing fracturing operationKey words:interwell communication;fracturing fracture;earth stress;sand production mechanism;Xinchang gas field;upper Shaximiao gas reservoirStudy and application of fracture propagation model of multi

21、ple sand fracturingLIU Chunlin1,2,WANG Rui3(1China University of Petroleum,Beijing102249,China;2Xian Shiyou University,Xian,Shaanxi710065,China;3Jidong Oilfield Company,PetroChina,Tangshan,Hebei063000,ChinaAbstract:In multiple sand fracturing process,the height of sand bank has certain influence on

22、fluid flow in fractures and subse-quent proppant settlementA pseudo3D model is built to predict fracture propagation in multiple sand fracturing process through nu-merical simulationThe model includes continuity equation,pressure drop equation,and fracture width and height equation of frac-turing fl

23、uid flowing in fracturesThe pressure drop equation is based on the plate flow theory and mechanic equilibrium principle, and its difference from conventional pressure drop equation is that it takes the effect of sand bank height on fluid flow into accountThe computation shows that multiple fracturin

24、g is more effective in increasing production than conventional fracturingField test shows that multiple fracturing is an effective reservoir stimulation method and has significant meaning to improving oil productionKey words:fracturing;multiple sand input;sand bank;fracture;pressure drop;Hua152block

25、 of the Changqing oilfield Productivity study of lowvelocity nonlinear flow in low permeability tight gas reservoirsSONG Hongqing1,HE Dongbo2,LOU Yu1,YI Huaijian1,ZHU Weiyao1(1University of ScienceTechnology Beijing,Beijing100083,China;2Research Institute of Petroleum Exploration and Development,Pet

26、roChina,Beijing100083,ChinaAbstract:Low permeability tight gas reservoirs are classified into three categories according to formation water occurrencesMathe-matical models are established for seepage flow in different reservoirs by taking account of slippage effect,stress sensitivity and threshold p

27、ressure gradient respectively and simultaneouslyProductivity formulas are derived for lowvelocity nonlinear flow in the three categories of low permeability tight gas reservoirsNumerical analysis shows that,compared with traditional Darcy flow,the productivity of low velocity nonlinear flow in low p

28、ermeability tight gas reservoirs is quite different under different flow regimesWhen producing pressure drop is big,stress sensitivity has greater effect on gas well productivityIn the production process of low permeability tight gas reservoirs,productivity equations corresponding to specific flow r

29、egime shall be chosen according to the water content of a gas reservoirLarge drawdown pressure and accelerated production shall be avoidedKey words:low permeability tight gas reservoirs;lowvelocity nonlinear flow;slippage effect;stress sensitivity;mathematical model;productivity equationNumerical si

30、mulation of the buried hill reservoir in the Sudeerte oilfieldWU Wei(Daqing Oilfield Company Limited,PetroChina,Daqing,Heilongjiang163712,ChinaAbstract:The influence of different fracture properties on buried hill reservoir development response has been simulated with a dual porosity dualpermeabilit

31、y model by using time variant techniqueThe trend of oil and water migration and remaining oil distri-bution is analyzed and predicted for buried hill reservoir under the condition of fracture influencePrediction of the development re-sponses of different well patterns and water injection schemes can

32、 guide oilfield infill modificationA modification plan of well pat-tern and water injection scheme has been proposed according to the geologic feature of the Sudeerte oilfield and has obtained good development resultKey words:fractured buried hill reservoir;dual media;numerical simulation;developmen

33、t modification;Sudeerte oilfieldA new computing method of gas compressibility factorGUAN Hongxiang1,DUAN Guoxi2,QI Tao1,LI Wei1,LI Weichao1(1CNOOC Research Institute,Beijing100027,China;2Tianjin Branch of CNOOC,Tianjin300452,China Abstract:Compressibility factor is one of the important parameters of

34、 natural gasTraditional computing method has big error incalculation of superhigh pressure natural gas This paper matches the traditional compressibility factor with the experimental data of superhigh pressure gas compressibility factor，and obtains a formula of compressibility factor for both mid lo

35、w and high pressure conditions The computation shows that the average error is 3 3% for low pressure interval and 2 5% for high pressure interval Gas well pressure has been calculated by applying this formula，and high calculation accuracy has been achieved Key words： compressibility factor； natural

36、gas； conventional gas well； high temperature high pressure gas well； computing method An approach to similarity method of experiment of remaining oil distribution after water flooding WANG Jin lin，TIAN Jin jie，WANG Jing bo，HUANG Bo，LIU Fu hai （ CNOOC Energy Technology Services Limited，Tianjin 300452

37、，China） Abstract： The similarity methods of physical simulation of oil displacement experiment generate many similarity criteria The requirement on model construction is relatively high and the realization is difficult According to the research on remaining oil distribution after water flooding and

38、development performance，this paper combines geometric method with equation method，recognizes that the real velocity （ movement velocity） of seepage flow is the same and the geometry changes in proportion when the major features of core and fluid are the same，thus obtained a relatively simple method

39、of similarity transformation This method effectively averts the difficulty brought by rigorously considering the similarity of geometric thickness，and needs not to select and combine different system parameters，thereby greatly reduced the difficulty of similarity transformation Key words： equality o

40、f velocity； similarity criteria； geometric method； equation method； Bohai SZ36 1 oilfield The effect of structural dip on gas injection response in condensate gas reservoir 2 CHEN Xiao fan1 ，YANG Cheng bo1， ，YANG Jian3 （ 1 State Key Laboratory of Oil Gas Reservoir Geology and Exploitation， Southwest

41、 Petroleum University，Chengdu，Sichuan 610500，China； 2 Star Petroleum Company，SINOPEC，Beijing， 100083，China； 3 Southwest Petroleum Company，SINOPEC，Chengdu，Sichuan 610081，China） Abstract： Structural dip is a critical factor affecting gas injection response Condensate gas reservoirs with different stru

42、ctural dip have different rules of oil / gas / water seepage flow and production characteristics， therefore different development strategies and measures are required Numerical simulation has been conducted to compare the effect of different structural dip on gas injection response based on fluid pa

43、rameters of the Dalaoba condensate gas reservoir to research into the rule of condensate oil recovery factor It is suggested that more injectors shall be placed in structural high and more producers shall be placed in structural low This will be helpful to improving the development effect of cyclic

44、gas injection for condensate gas reservoir Key words： condensate gas reservoir； gas injection； structural dip； anisotropy； condensate oil； recovery factor； numerical simulation； Dalaoba Structure 2 condensate gas reservoir Experimental study of formation damage in ultra low permeability sandstone re

45、servoirs 2 2 HE Wen xiang1， ，YANG Yi qian1， ，MA Chao ya3 ，ZHU Sheng ju1 （ 1 Yangtze University，Jingzhou，Hubei 434023，China； 2 MOE Key Laboratory of Oil and Gas Resources and Exploration Technoloy， Yangtze University，Jingzhou，Hubei 434023，China； 3 Changqing Oilfield Company，PetroChina，Yan an，Shaanxi

46、717606，China） Abstract： Formation damage during the process of water flooding has been analyzed for ultra low permeability sandstone reservoirs under different permeability conditions，and rational development strategies have been worked out The cores of ultra low permeability from the Geng 43 well b

47、lock and the Middle Baima block in the Changqing Oilfield have been taken as the samples to analyze formation sensitivity，Jamin effect，water lock effect and water injection damage The general law of formation damage in ultra low permeability reservoirs and its relationship with permeability has been

48、 generalized Measures of avoiding formation sensitivity damage and improving water quality have been proposed The study results will provide guidance for the development of similar oilfields Key words： sensitivity； water injection damage； ultra low permeability reservoir； water lock effect； Jamin effect； Geng 43 well block； Middle Baima well block Study on catalytic aquathermolysis and enhance