吳家文,左松林,趙秀娟,費(fèi)建平,劉洪濤,王起超
(1.中國(guó)石油大慶油田有限責(zé)任公司勘探開(kāi)發(fā)研究院,黑龍江大慶163712;2.中國(guó)石油大慶油田有限責(zé)任公司大慶鉆探工程公司,黑龍江大慶163413;3.中國(guó)石油大慶油田有限責(zé)任公司第二采油廠,黑龍江大慶163414;4.中國(guó)石油大慶油田有限責(zé)任公司測(cè)試技術(shù)服務(wù)分公司,黑龍江大慶163511)
喇嘛甸中塊層系井網(wǎng)調(diào)整技術(shù)經(jīng)濟(jì)界限
吳家文1,左松林1,趙秀娟1,費(fèi)建平2,劉洪濤3,王起超4
(1.中國(guó)石油大慶油田有限責(zé)任公司勘探開(kāi)發(fā)研究院,黑龍江大慶163712;2.中國(guó)石油大慶油田有限責(zé)任公司大慶鉆探工程公司,黑龍江大慶163413;3.中國(guó)石油大慶油田有限責(zé)任公司第二采油廠,黑龍江大慶163414;4.中國(guó)石油大慶油田有限責(zé)任公司測(cè)試技術(shù)服務(wù)分公司,黑龍江大慶163511)
為了確定層系井網(wǎng)調(diào)整的技術(shù)經(jīng)濟(jì)界限,以動(dòng)態(tài)分析、理論計(jì)算、數(shù)值模擬和經(jīng)濟(jì)評(píng)價(jià)相結(jié)合的方法,研究了喇嘛甸中塊層系井網(wǎng)調(diào)整的井距、縱向滲透率變異系數(shù)、層系組合厚度和層系組合跨度等參數(shù)的技術(shù)經(jīng)濟(jì)界限。其中,通過(guò)動(dòng)態(tài)分析方法研究在現(xiàn)井網(wǎng)條件下逐步加密時(shí)水驅(qū)控制程度的變化規(guī)律;應(yīng)用數(shù)值模擬技術(shù)研究井距與采收率關(guān)系,綜合確定合理井距;在合理井距研究的基礎(chǔ)上,通過(guò)概念模型確定滲透率變異系數(shù)界限;運(yùn)用經(jīng)濟(jì)評(píng)價(jià)方法,依據(jù)盈虧平衡原理,計(jì)算合理井距、不同油價(jià)下的合理層系組合厚度;基于井距和層系組合厚度界限,通過(guò)理論計(jì)算,確定合理層系組合跨度;通過(guò)數(shù)值模擬和經(jīng)濟(jì)評(píng)價(jià)方法確定井網(wǎng)調(diào)整后的界限。結(jié)果表明,當(dāng)喇嘛甸中塊合理井距為150 m時(shí),合理層系組合厚度為7.5 m,合理層系組合跨度為50 m,合理縱向滲透率變異系數(shù)為0.7。
層系組合厚度經(jīng)濟(jì)界限合理井距層系組合跨度縱向滲透率變異系數(shù)
目前,喇嘛甸中塊已經(jīng)進(jìn)入特高含水開(kāi)發(fā)階段,層系井網(wǎng)交叉嚴(yán)重,平面上井距不均,波及系數(shù)低;縱向上層間干擾較大,注水效果差、動(dòng)用程度低、含水率上升快。通過(guò)局部的單井挖潛和措施調(diào)整不能從根本上解決喇嘛甸中塊的層系井網(wǎng)問(wèn)題,需要進(jìn)行層系井網(wǎng)的調(diào)整與重組,表現(xiàn)為平面上縮小井距,提高注水效果;縱向上縮小井段,減小層間矛盾。層系井網(wǎng)的調(diào)整,需要技術(shù)經(jīng)濟(jì)界限研究的支持。鞠洪文等分別應(yīng)用理論計(jì)算、動(dòng)態(tài)分析等方法研究了合理井距的確定方法[1-3]。對(duì)于滲透率變異系數(shù)的研究,目前多集中在算法對(duì)比與分析方面[4-6],也有關(guān)于滲透率變異系數(shù)與驅(qū)油效果的研究[7-9],但未涉及技術(shù)經(jīng)濟(jì)界限研究,層系組合厚度、層系組合跨度等技術(shù)指標(biāo)界限的研究相對(duì)較少,不具有系統(tǒng)性[10-11]。筆者利用動(dòng)態(tài)分析與數(shù)值模擬相結(jié)合的方法確定喇嘛甸中塊的合理井距,并以合理井距為基礎(chǔ),綜合運(yùn)用動(dòng)態(tài)分析、理論計(jì)算、數(shù)值模擬和經(jīng)濟(jì)評(píng)價(jià)等方法確定合理縱向滲透率變異系數(shù)、合理層系組合厚度和合理層系組合跨度。
1.1合理井距
根據(jù)研究區(qū)地質(zhì)特征,繪制各小層的沉積相帶圖,將現(xiàn)有井網(wǎng)在沉積相帶圖上標(biāo)注出來(lái),根據(jù)井網(wǎng)分布、油水井在小層的射孔情況、小層相帶分布,綜合計(jì)算現(xiàn)有井網(wǎng)條件下小層的水驅(qū)控制程度;然后,應(yīng)用相同的方法,把現(xiàn)有井網(wǎng)逐步加密,研究不同井距下的水驅(qū)控制程度,分析井距與水驅(qū)控制程度的關(guān)系。研究結(jié)果表明,有效厚度小于1 m,滲透率小于100×10-3μm2的3類(lèi)油層的井距為150~200 m時(shí),砂體有效控制程度較高,當(dāng)井距大于150 m時(shí),砂體有效控制程度下降較快。
根據(jù)研究區(qū)地質(zhì)模型,采用數(shù)值模擬方法,部署不同井距的五點(diǎn)法井網(wǎng),研究井距與采收率的關(guān)系。結(jié)果表明,當(dāng)井距大于150 m時(shí),隨著井距的增加,采收率下降較快,因此確定喇嘛甸中塊合理井距為150 m。
1.2合理縱向滲透率變異系數(shù)
縱向滲透率變異系數(shù)主要反映縱向非均質(zhì)性,對(duì)開(kāi)發(fā)效果影響較大??v向滲透率變異系數(shù)大的井,其開(kāi)發(fā)效果較差,主要表現(xiàn)為油井含水率高、水井吸水差和動(dòng)用程度低??v向滲透率變異系數(shù)計(jì)算式為
其中
式中:VK為縱向滲透率變異系數(shù);σ為標(biāo)準(zhǔn)偏差;-K為平均滲透率,10-3μm2;n為縱向上的小層數(shù);i為序列數(shù);Ki為第i個(gè)小層的滲透率,10-3μm2。
采用數(shù)值模擬方法,建立縱向10個(gè)小層的概念模型,平面為均質(zhì),縱向?yàn)榉蔷|(zhì),保持滲透率級(jí)差不變(即最大滲透率層和最小滲透率層滲透率不變),通過(guò)調(diào)整中間層滲透率獲得不同的縱向滲透率變異系數(shù),研究縱向滲透率變異系數(shù)與采收率的關(guān)系(圖1)。結(jié)果表明,縱向滲透率變異系數(shù)每增加0.1,采收率就會(huì)下降0.7個(gè)百分點(diǎn),但當(dāng)縱向滲透率變異系數(shù)大于0.7以后斜率變??;根據(jù)縱向滲透率變異系數(shù)對(duì)采收率影響,縱向滲透率變異系數(shù)應(yīng)控制在0.7以內(nèi)。
圖1 不同滲透率級(jí)差下縱向滲透率變異系數(shù)對(duì)采收率的影響Fig.1 Influence of longitudinal permeability variation coefficient on recovery efficiency at different permeability ratios
1.3合理層系組合厚度
利用經(jīng)濟(jì)評(píng)價(jià)方法,依據(jù)盈虧平衡原理,以研究區(qū)現(xiàn)有井網(wǎng)為基礎(chǔ),計(jì)算不同井距、不同油價(jià)的最低累積產(chǎn)油量界限,并在此基礎(chǔ)上根據(jù)容積法反推不同井距、不同油價(jià)的層系組合厚度界限。結(jié)果表明,當(dāng)合理井距為150 m、油價(jià)為80美元/桶時(shí),層系組合厚度界限為7.5 m(圖2)。
1.4合理層系組合跨度
通過(guò)分析層系數(shù)與層系組合跨度、縱向滲透率變異系數(shù)、層系頂?shù)灼屏褖毫Σ钪g的關(guān)系,以層系組合厚度作為約束條件,綜合確定層系段數(shù)和層系組合跨度界限。根據(jù)經(jīng)驗(yàn)方法[12]計(jì)算可知,層系組合跨度每增加100 m,注水壓力與破裂壓力的差值增加0.3 MPa。破裂壓力和注水壓力隨埋深的關(guān)系表現(xiàn)為:埋深為800 m時(shí),破裂壓力與注水壓力較接近;埋深為1 400 m時(shí),破裂壓力與注水壓力的差值變大。因此,當(dāng)層系組合跨度較大時(shí),如果注水壓力剛剛滿足頂層的注水要求,那么層系底部小層的注水壓力則與實(shí)際需要差距較大,造成底部小層吸水差,油層難以動(dòng)用,這也是層系組合跨度大時(shí)油層開(kāi)采效果差的原因之一。
圖2 喇嘛甸中塊不同油價(jià)下的累積產(chǎn)油量和層系組合厚度界限Fig.2 Cumulative oil output and combination thickness at different oil prices in Lazhong block
將研究區(qū)3類(lèi)油層劃分為1~5套層系,計(jì)算每套層系的組合跨度、層系組合厚度、縱向滲透率變異系數(shù)和層系頂?shù)灼屏褖毫Σ?。從圖3可以看出,以層系組合厚度7.5 m作為約束條件,從層系組合厚度看,研究區(qū)層系劃分應(yīng)小于等于5段;從層系組合跨度看,當(dāng)層系劃分為3~4段時(shí)符合層系組合厚度界限的要求。根據(jù)上述研究成果,確定層系數(shù)為3~4段,層系組合跨度為50 m,層系頂?shù)灼屏褖毫Σ顬?.15 MPa左右。從層系組合厚度與縱向滲透率變異系數(shù)之間的關(guān)系(圖4)可以看出,當(dāng)層系數(shù)為3~4段時(shí),縱向滲透率變異系數(shù)小于0.7,滿足縱向滲透率變異系數(shù)的界限要求。
圖3 喇嘛甸中塊層系組合跨度與層系組合厚度和層系頂?shù)灼屏褖毫Σ铌P(guān)系Fig.3 Relationship between combination span and combination thickness,bursting pressure difference in Lazhong block
圖4 喇嘛甸中塊層系組合厚度與縱向滲透率變異系數(shù)關(guān)系Fig.4 Relationship between combination thickness and longitudinal permeability variation coefficient in Lazhong block
井距、縱向滲透率變異系數(shù)、層系組合跨度、層系組合厚度的界限值確定后,需制定層系井網(wǎng)調(diào)整后的新井初始產(chǎn)油量、初始含水率的界限值。應(yīng)用數(shù)值模擬技術(shù),結(jié)合經(jīng)濟(jì)評(píng)價(jià)方法,確定研究區(qū)不同油價(jià)、不同井距下的初始產(chǎn)油量界限和初始含水率界限(圖5,圖6)。從圖5和圖6可見(jiàn),當(dāng)合理井距為150 m、油價(jià)為80美元/桶時(shí),其新井初始產(chǎn)油量界限為1.42 t/d,新井初始含水率界限為92.0%。
圖5 喇嘛甸中塊不同井距與新井初始產(chǎn)油量界限關(guān)系Fig.5 Relationship between initial oil rate of new well and different well spacings in Lazhong block
圖6 喇嘛甸中塊不同井距與新井初始含水率界限關(guān)系Fig.6 Relationship between initial water cut of new well and different well spacings in Lazhong block
研究層系井網(wǎng)技術(shù)經(jīng)濟(jì)界限的方法,立足區(qū)塊現(xiàn)狀,以經(jīng)濟(jì)效益為中心,綜合應(yīng)用了動(dòng)態(tài)分析、理論計(jì)算、數(shù)值模擬、經(jīng)濟(jì)評(píng)價(jià)等多種手段,多種指標(biāo)相互約束,避免了多指標(biāo)之間的矛盾。但是,各技術(shù)經(jīng)濟(jì)指標(biāo)之間相互影響,比如層系組合跨度與縱向滲透率變異系數(shù)之間存在一定的相關(guān)性,需要深入研究。此外,制定界限時(shí),還應(yīng)考慮采油速度、措施工作量等其他指標(biāo),在今后的工作中繼續(xù)深入研究。
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編輯王星
Technical and economic boundaries on formation and well pattern adjustment in Lazhong block
Wu Jiawen1,Zuo Songlin1,Zhao Xiujuan1,F(xiàn)ei Jianping2,Liu Hongtao3,Wang Qichao4
(1.Exploration and Development Research Institute of Daqing Oilfield Company Ltd.,PetroChina,Daqing City,Heilongjiang Province,163712,China;2.Daqing Drilling&Exploration Engineering Company,Daqing Oilfield Company Ltd.,PetroChina,Daqing City,Heilongjiang Province,163413,China;3.No.2 Oil Production Plant of Daqing Oilfield Company Ltd.,PetroChina,Daqing City,Heilongjiang Province,163414,China;4.Well Logging Services Branch Company of Daqing Oilfield Company Ltd.,PetroChina,Daqing City,Heilongjiang Province,163511,China)
In order to determine the technical and economic boundaries of well pattern adjustment,technical and economic boundaries of well spacing,longitudinal permeability variation coefficient,and thickness and span of layer series combination were studied through dynamic analysis,theoretical calculation,numerical simulation and economic evaluation.The variation waterflood controlling level with well spacing was studied through dynamic analysis.Relationship between recovery efficiency and well spacing was studied using numerical simulation to determine rational well spacing.Limit of permeability variation coefficient was obtained by conceptual model.Rational combination thickness of layer series with different well spacings and oil prices was calculated based on profit and loss balance principle using economic evaluation method. Combination series span was determined through theoretical calculation based on well spacing and combination thickness of layer series.Initial oil rate and water cut after adjustment was calculated using numerical simulation and economic evaluation.Reasonable well spacing of Lazhong block is 150 m,and reasonable combination thickness is 7.5 m.The combination span is 50 m,and the longitudinal permeability variation coefficient is 0.7.
thickness of layer series combination;economic boundaries;rational well spacing;span of layer series combi-nation;longitudinal permeability variation coefficient
TE313.5
A
1009-9603(2015)05-0113-04
2015-07-15。
吳家文(1975—),男,山東陵縣人,高級(jí)工程師,博士,從事層系井網(wǎng)調(diào)整和方案編制等研究。聯(lián)系電話:13836991327,E-mail:wjw253517@163.com。
國(guó)家自然科學(xué)基金項(xiàng)目“低滲透油藏提高驅(qū)油效率的機(jī)理研究”(50634020)。