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首页> 外文会议>Society of Core Analysts Symposium >ENHANCED CHEMICAL WEAKENING OF CHALK DUE TO INJECTION OF CO2 ENRICHED WATER Korsnes, R.I.*, Madland, M.V.*, Vorland, K.A.N*, Hildebrand-Habel, T.*, Kristiansen, T.G.**, and Hiorth, A.*** *University of Stavanger, 4036 Stavanger, Norway, ** BP Norway, *** IRIS research This paper was prepared for presentation at the International Symposium of the Society of Core Analysts held in Abu Dhabi, UAE 29 October-2 November, 2008
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ENHANCED CHEMICAL WEAKENING OF CHALK DUE TO INJECTION OF CO2 ENRICHED WATER Korsnes, R.I.*, Madland, M.V.*, Vorland, K.A.N*, Hildebrand-Habel, T.*, Kristiansen, T.G.**, and Hiorth, A.*** *University of Stavanger, 4036 Stavanger, Norway, ** BP Norway, *** IRIS research This paper was prepared for presentation at the International Symposium of the Society of Core Analysts held in Abu Dhabi, UAE 29 October-2 November, 2008

机译：由于注射CO2富含水Korsnes，Ri *，Madland，MV *，Vorland，Kan *，Hildebrand-Habel，T. *，Kristiansen，TG **和Hiorth Stavanger大学，4036 Stavanger，挪威，** BP挪威，***虹膜研究论文是为2008年10月29日阿布扎比举行的核心分析师协会国际研讨会的介绍

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Chalk deformation and especially the so called water weakening effect induced by seawater injection, which caused a dramatic increase in subsidence rate in the early 90s at the Ekofisk field, has been extensively studied worldwide. Potential CO2 injection into depleted chalk reservoirs will lead to acidification of the formation brine or pore-water itself; since the solubility of carbonates is strongly pH dependent, enhanced water weakening should thus be expected. CO2 related chemical weakening of chalk has been experimentally verified at the laboratory of University of Stavanger. By use of a standard triaxial cell, series of chalk cores were isotropically loaded beyond yield and thereafter left to creep at constant effective stresses between 12 and 14 MPa. All experiments were performed at ambient temperature, and the cores were exposed to alternating flooding with and without CO2 enriched fluids, distilled water, seawater, and/or seawater with 4 times the concentration of SO_4~(2-), at flow rates of 0.05 ml/min, i.e., 2 pore volumes (PV) per day, and a backpressure of 10 bar. The tested chalk cores exposed to CO2 enriched brines showed an average increase in creep strain rates of 19% compared to CO2 enriched distilled water. Increasing the partial pressure of CO2 in the brine leads to a higher equilibrium concentration of Ca~(2+). An increased equilibrium concentration of Ca~(2+) triggers two processes: Firstly, dissolution of the calcitic (CaCO3) matrix, and secondly brine supersaturation with respect to gypsum (CaSO4×2H20). When gypsum is precipitated, more Ca~(2+) needs to go into solution for the water to be in equilibrium with the core. Thus, the dissolution and water weakening effect of the chalk is not only dependent on the pH, but also the sulphate concentration in the brine. From our work, it seems that long time storage of CO2 could be challenging in chalk. One may also conclude that CO2 used as an EOR fluid in chalk can trigger significantly increased compaction. The enhanced weakening to be expected when chalk is exposed to CO2 injection will thus be governed by the reservoir conditions – temperature, in situ stresses, CO2 phase and the fluids in which CO2 dissolves. In order to successfully implement a CO2 flood or storage project in chalk, the aspects related to significant compaction, as well as well design and surface facilities, topics not covered in this study, need to be considered accordingly. If these issues are properly managed the compaction can result in significant enhanced oil recovery from chemically induced compaction.
机译：粉笔变形尤其是海水注射诱导的所谓水弱效应，这在全世界都会广泛研究了EKOFISK领域的90年代初期陷入急剧增加。潜在的CO2注射到耗尽的粉笔储层将导致形成盐水或孔隙自身的酸化;由于碳酸酯的溶解度是强烈的pH依赖性，因此应该预期增强的水弱化。 CO2相关化学弱化粉笔已经在斯塔万格大学实验室进行了实验验证。通过使用标准三轴电池，一系列粉末芯被同向上，超过产量，然后留在12至14MPa之间的恒定有效应力下蠕变。所有实验均在环境温度下进行，并且核心暴露于交替的洪水，而无需CO 2富集的流体，蒸馏水，海水和/或海水，其流速为0.05的流速，其流速为0.05 ml / min，即每天2个孔体积（pv），以及10巴的背压。与CO 2富集的蒸馏水相比，暴露于CO 2富集的盐水的测试粉核的蠕变应变率平均增加了19％。增加盐水中CO 2的分压导致Ca〜（2+）的更高平衡浓度。增加的Ca〜（2+）触发的平衡浓度增加了两种方法：首先，钙质（CaCO 3）基质的溶解和相对于石膏（CasO4×2H20）的第二盐水过饱和。当石膏沉淀时，更多CA〜（2+）需要进入水的溶液与核心平衡。因此，粉笔的溶解和水弱效应不仅依赖于pH，而且含有盐水中的硫酸盐浓度。从我们的工作中，似乎很长时间储存​​二氧化碳可能是粉笔挑战。还可以得出结论，用作粉笔中的EOR流体的二氧化碳可以触发显着增加的压实。因此，当粉笔暴露于CO2注射时，预期的增强弱化将由储层条件 - 温度，原位应力，CO 2和CO2溶解的流体管辖。为了成功地实施二氧化碳洪水或储存项目，与大量压实相关的方面，以及本研究中未涵盖的主题，需要相应地考虑。如果妥善管理这些问题，则压实可能导致从化学诱导的压实中产生显着的增强的油回收。

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