-
摘要: 針對裂隙性儲層水力壓裂行為中出現的圍巖維護、增透效率與地下水害防治等實際問題,本文對多場多相耦合作用下起裂壓力控制機制,以及壓裂性評價展開了深入研究。首先分析了射孔集中力對原始應力場的改造作用;其次,考慮壓裂液在儲層原生裂隙中的滲透作用;最后,基于斷裂力學強度準則建立了水平井起裂壓力計算模型。根據模型分析了儲層裂隙場幾何參數對起裂壓力的控制作用,提出了裂隙場特征參數的概念。研究結果表明,水平井水力壓裂是流固多相在射孔應力場、壓裂液滲流場以及儲層裂隙場耦合空間內相互作用過程,裂隙場特征參數對起裂壓力的大小起著主導控制作用,其中最大控制因素為儲層隙寬,且當儲層隙寬在200~700 μm區間內時,水力壓裂對改善其滲透性能才有實際意義,從而解決了裂隙性儲層起裂壓力的定量化與壓裂性評判問題。經實例計算與對比發現,蘇里格氣田東區H8段的砂巖儲層,起裂壓力的理論值與實測值契合度較高,壓裂后的產能也十分理想,從而驗證了模型的正確性,可以為水平井壓裂施工提供理論依據。Abstract: There are many practical engineering problems in the hydraulic fracturing of crack reservoirs, such as the maintenance of wall rock, the efficiency of reservoir's permeability and the prevention of groundwater hazard. In this paper, the control mechanism of fracture pressure under multi-field and multi-phase coupling in horizontal wells and the fracturing evaluation of crack reservoirs were studied deeply to address these issues. Firstly, the transformation effect of the perforation concentration on the original stress field was analyzed. Secondly, the permeability of fracturing fluid in the primary fractures was considered. Finally, based on the strength principle of fracture mechanics, the calculation model of fracture pressure for horizontal wells in the reservoir was established. Furthermore, the influence of the spatial geometric parameters of the fracture field on the initiation pressure was analyzed, and the concept of the characteristic parameters of the fracture field was proposed. The results indicate that the coupling of fluid-solid multiphase in the fields of perforation stress, fracturing fluid permeation and original fracture leads to horizontal well hydraulic fracturing, and the characteristic parameter of fracture field plays a leading role in controlling the initiation pressure. Among them, the biggest controlling factor on initiation pressure is crack width. When the crack width of reservoir is within 200–700 μm, hydraulic fracturing has practical significance for improving reservoir permeability, which solves the problem about the quantification of initiation pressure and the fracturing evaluation in crack reservoirs. By calculating initiation pressure and contrasting to engineering example, it is found that the productivity of the sandstone reservoir is very ideal in the H8 section of the eastern Sulige gas field after hydraulic fracturing, and the theoretical value of fracture initiation pressure is in good agreement with the measured value, which verifies the correctness of the model. These can provide theoretical basis for fracturing construction of horizontal wells.
-
Key words:
- horizontal well /
- many field and heterogeneous /
- cracking medium /
- cracking pressure /
- wide of fracture
-
表 1 焦作礦區裂隙場特征參數統計表
Table 1. Characteristic parameter statistics table of fracture field in Jiaozuo mining areas
Number Crack half length,
a / mAverage crack width,
b / mCrack average distance,
s/mCrack surface roughness,
λ[22]Rock permeability coefficient,
K/ (m·s–1)Fracture toughness constant,
KIC / (MPa·m1/2)1 0.01 4.0×10–4 5.26×10–3 1/12 1.24×10–2 0.118 2 0.018 2.3×10–4 1.22×10–3 1/12 1.02×10–2 0.212 3 0.004 3.8×10–4 3.85×10–3 1/12 1.46×10–2 0.047 4 0.015 4.0×10–4 5.88×10–3 1/12 1.11×10–2 0.175 5 0.025 3.0×10–4 2.17×10–3 1/12 1.27×10–2 0.295 表 2 裂縫控制參數影響度分析表
Table 2. Sensitivity analysis table of crack control parameter influence
i Reference value Fluctuation range of uncertainties b / μm 342 –100% –80% –60% –40% –20% 0 20% 40% 60% 80% 100% Db / (N·m–1) 100 0 0 0.41 4.67 26.2 100 299 753 1679 3403 6403.2 a / cm 1.44 –100% –80% –60% –40% –20% 0 20% 40% 60% 80% 100% Da / (N·m–1) 100 –– 2501.3 625.3 277.9 152.6 100 69.5 51.1 39.1 30.9 25.1 s / mm 3.676 –100% –80% –60% –40% –20% 0 20% 40% 60% 80% 100% Ds / (N·m–1) 100 –– 500 250 166.7 125.0 100 83.3 71.4 62.5 55.6 50.0 Note:Db, Da and Da are crack control parameters related to b, a and s, respectively. 表 3 起裂壓力理論值與實測值對比表
Table 3. Comparison table of theoretical and measured values of cracking pressure
Burial depth / m Perforation half pitch, L / m Wellbore radius,
Rw / mCrack field characteristic parameters, D /(N·m–1) Poisson ratio, μ Initiation pressure / MPa Theoretical value Actual value 3190 2 0.2 7.653×104 0.306 48.11 52.94 3200 2 0.2 7.653×104 0.251 49.18 47.06 3210 2 0.2 7.653×104 0.305 50.25 52.95 3220 2 0.2 7.653×104 0.250 51.32 50.21 3230 2 0.2 7.653×104 0.260 52.39 48.85 3240 2 0.2 7.653×104 0.319 53.46 53.00 259luxu-164 -
參考文獻
[1] Cui F, Liu X H. Research on control technology of hydraulic fracturing roof in fully-mechanized mining face. Coal Sci Technol, 2019, 47(9): 172崔峰, 劉星合. 綜采工作面水力壓裂頂板控制技術研究. 煤炭科學技術, 2019, 47(9):172 [2] Zhang J, Yang T, Suo Y L, et al. Forecast model for roof water inrush in Anshan coal mine based on coupling evaluation. J Xi’an Univ Sci Technol, 2018, 38(4): 569張杰, 楊濤, 索永錄, 等. 基于耦合評價的安山煤礦頂板突水預測模型研究. 西安科技大學學報, 2018, 38(4):569 [3] Sun K, Wang Y, Li C, et al. Mechanism of roof separation water disaster in thick coal seam. J Henan Polytech Univ Nat Sci, 2018, 37(2): 14孫魁, 王英, 李成, 等. 巨厚煤層頂板離層水致災機理研究. 河南理工大學學報: 自然科學版, 2018, 37(2):14 [4] Zhang Q, Ge C G, Li W, et al. A new model and application of coalbed methane high efficiency production from broken soft and low permeable coal seam by roof strata-in horizontal well and staged hydraulic fracture. J China Coal Soc, 2018, 43(1): 150張群, 葛春貴, 李偉, 等. 碎軟低滲煤層頂板水平井分段壓裂煤層氣高效抽采模式. 煤炭學報, 2018, 43(1):150 [5] Yin L M, Ma K, Chen J T, et al. Mechanical model on water inrush assessment related to deep mining above multiple aquifers. Mine Water Environ, 2019, 38(4): 827 doi: 10.1007/s10230-019-00623-3 [6] Wu X P, Zhang Q. Research on controlling mechanism of fracture propagation of multi-stage hydraulic fracturing horizontal well in roof of broken soft and low permeability coal seam. Nat Gas Geosci, 2018, 29(2): 268巫修平, 張群. 碎軟低滲煤層頂板水平井分段壓裂裂縫擴展規律及控制機制. 天然氣地球科學, 2018, 29(2):268 [7] Zheng G, Xu X B, He Y, et al. Mechanism of Ordovician limestone water inrush from the floor of caving mining face in thick coal seam and water hazard detection technology of nearly horozontal borehole. Coal Geol Explor, 2019, 47(Suppl 1): 7鄭綱, 徐小兵, 何淵, 等. 厚煤層放頂煤開采底板突水機理及水害探查技術. 煤田地質與勘探, 2019, 47(增刊1): 7 [8] Ding Y, Liu X J, Luo P Y. Research on influential factors of initiation pressure in fracture formation for perforated boreholes. Appl Math Mech, 2018, 39(7): 811丁乙, 劉向君, 羅平亞. 裂縫性儲層射孔井起裂壓力影響因素分析. 應用數學和力學, 2018, 39(7):811 [9] Fan Y, Zhao Y L, Zhu Z M, et al. Theoretical study of break down pressures and fracture initiation angles based on model containing wellbore and perforations. J Cent South Univ Sci Technol, 2019, 50(3): 669范勇, 趙彥琳, 朱哲明, 等. 基于井筒-射孔模型的地層破裂壓力及起裂角的理論研究. 中南大學學報: 自然科學版, 2019, 50(3):669 [10] Liu D T, Shen Z Z, Xu L Q, et al. Experimental study on critical internal water pressure of hydraulic fracturing of fractured rock mass. South-to-North Water Transfers Water Sci Technol, 2018, 16(2): 140劉得潭, 沈振中, 徐力群, 等. 裂隙巖體水力劈裂臨界水壓力試驗研究. 南水北調與水利科技, 2018, 16(2):140 [11] Deng S, Zhu Z M, Wang L, et al. Study on the influence of in-situ stresses on dynamic fracture behaviors of cracks. Chin J Rock Mech Eng, 2019, 38(10): 1989鄧帥, 朱哲明, 王磊, 等. 原巖應力對裂紋動態斷裂行為的影響規律研究. 巖石力學與工程學報, 2019, 38(10):1989 [12] Lu Y, Li H T, Lu C, et al. Predicting the fracture initiation pressure for perforated water injection wells in fossil energy development. Int J Hydrogen Energy, 2019, 44(31): 16257 doi: 10.1016/j.ijhydene.2019.04.208 [13] Zhang F, Ma G, Liu X, et al. Experimental study on initiation pressure and mechanism of fracture propagation of hydraulic fracturing in coal and rock mass. Coal Geol Explor, 2017, 45(6): 84 doi: 10.3969/j.issn.1001-1986.2017.06.014張帆, 馬耕, 劉曉, 等. 煤巖水力壓裂起裂壓力和裂縫擴展機制實驗研究. 煤田地質與勘探, 2017, 45(6):84 doi: 10.3969/j.issn.1001-1986.2017.06.014 [14] Cheng Y G, Lu Y Y, Ge Z L, et al. Influence of pore water pressure gradient on guiding hydraulic fracturing in underground coal mine. J Northeast Univ Nat Sci, 2017, 38(7): 1043程玉剛, 盧義玉, 葛兆龍, 等. 孔隙水壓力梯度對煤層導向壓裂控制影響. 東北大學學報: 自然科學版, 2017, 38(7):1043 [15] Ma T S, Peng N, Chen P, et al. Wellbore fracture initiation mechanical behavior in a horizontal shale gas well. J Southwest Petrol Univ Sci Technol Ed, 2019, 41(6): 87馬天壽, 彭念, 陳平, 等. 頁巖氣水平井井壁裂縫起裂力學行為研究. 西南石油大學學報: 自然科學版, 2019, 41(6):87 [16] Wen X L. Study on the Fracture Initiation and Propagation for Hydrajet-Fracturing[Dissertation]. Xi’an: Xi’an Shiyou University, 2011文賢利. 水力噴射壓裂裂縫起裂與擴展規律研究[學位論文]. 西安: 西安石油大學, 2011 [17] Zhang J C, Yin S X. Some technologies of rock mechanics applications and hydraulic fracturing in shale oil, shale gas and coalbed methane. J China Coal Soc, 2014, 39(8): 1691張金才, 尹尚先. 頁巖油氣與煤層氣開發的巖石力學與壓裂關鍵技術. 煤炭學報, 2014, 39(8):1691 [18] Li D Q, Zhang S C, Zhang S A, et al. Effect simulation of horizontal well fracturing through strata based on coal seam permeability anisotropy test. Acta Petrol Sin, 2015, 36(8): 988 doi: 10.7623/syxb201508010李丹瓊, 張士誠, 張遂安, 等. 基于煤系滲透率各向異性測試的水平井穿層壓裂效果模擬. 石油學報, 2015, 36(8):988 doi: 10.7623/syxb201508010 [19] Zhan M L, Cen J. Experimental and analytical study on hydraulic fracturing of cylinder sample. Chin J Rock Mech Eng, 2007, 26(6): 1173 doi: 10.3321/j.issn:1000-6915.2007.06.011詹美禮, 岑建. 巖體水力劈裂機制圓筒模型試驗及解析理論研究. 巖石力學與工程學報, 2007, 26(6):1173 doi: 10.3321/j.issn:1000-6915.2007.06.011 [20] Cheng J, Zhao S S. Fracture Mechanics. Beijing: Science Press, 2006程靳, 趙樹山. 斷裂力學. 北京: 科學出版社, 2006 [21] Li H X. Analysis on CBM occurrence characteristics of Jiulishan coalfield in Jiaozuo. Zhongzhou Coal, 2012, 34(9): 4 doi: 10.3969/j.issn.1003-0506.2012.09.002李宏欣. 焦作九里山井田煤層氣賦存特征分析. 中州煤炭, 2012, 34(9):4 doi: 10.3969/j.issn.1003-0506.2012.09.002 [22] Ye J P, Zhang S R, Ling B C, et al. Study on variation law of coalbed methane physical property parameters with seam depth. Coal Sci Technol, 2014, 42(6): 35葉建平, 張守仁, 凌標燦, 等. 煤層氣物性參數隨埋深變化規律研究. 煤炭科學技術, 2014, 42(6):35 [23] Ma X, Hao R F, Lai X A, et al. Field test of volume fracturing for horizontal wells in Sulige tight sandstone gas reservoirs. Petrol Explor Dev, 2014, 41(6): 742 doi: 10.11698/PED.2014.06.15馬旭, 郝瑞芬, 來軒昂, 等. 蘇里格氣田致密砂巖氣藏水平井體積壓裂礦場試驗. 石油勘探與開發, 2014, 41(6):742 doi: 10.11698/PED.2014.06.15 [24] Cui M M, Li J B, Wang Z X, et al. Characteristics of tight sand reservoir and controlling factors of high-quality reservoir at braided delta front: a case study from Member 8 of Shihezi formation in southwestern Sulige gas field. Acta Petrol Sin, 2019, 40(3): 279 doi: 10.7623/syxb201903003崔明明, 李進步, 王宗秀, 等. 辮狀河三角洲前緣致密砂巖儲層特征及優質儲層控制因素——以蘇里格氣田西南部石盒子組8段為例. 石油學報, 2019, 40(3):279 doi: 10.7623/syxb201903003 [25] Deng H F, Zhu M, Li J L, et al. Study of mode-Ⅰ fracture toughness and its correlation with strength parameters of sandstone. Rock Soil Mech, 2012, 33(12): 3585鄧華鋒, 朱敏, 李建林, 等. 砂巖I型斷裂韌度及其與強度參數的相關性研究. 巖土力學, 2012, 33(12):3585 [26] Zhou W L. Sedimentary and Diagenesis of Mawu _ (1-4) Subsection in Well Zhao54, Sulige District[Dissertation]. Chengdu: Southwest Petroleum University, 2016周文露. 蘇里格東區召54井區馬五_(1-4)亞段沉積與成巖作用研究[學位論文]. 成都: 西南石油大學, 2016 -