【作者】 计有权；

【导师】 杨天行；

【作者基本信息】 吉林大学 ， 地球探测与信息技术， 2005， 博士

【摘要】 将二氧化碳作为油藏提高采收率的驱油剂已研究多年,室内和现场试验都曾表明它是一种有效的驱油剂。它能够提高原油采收率的原因主要有以下几个方面。一方面是因为二氧化碳易溶于原油,这种特性可以起到如下三方面的作用。(1)使原油的体积增大,从而促使充满油的孔隙体积也增大,这为油在孔隙介质中流动提供了有利的条件。若随后地层注水,还可使油藏中的残余油量减小。(2)可使原油粘度降低,促使原油流动性提高,其结果是用少量的驱油剂就可达到一定的驱油效率。或换言之,用一定量的驱油剂就能达到较高的驱油效率。(3)能使毛细管的吸渗作用得到改善,从而使油层扫油范围扩大,使水、油的流动性保持平衡。另一方面是因为二氧化碳易溶于水,这种特性也可以起到如下三方面的作用。(1)使水的粘度有所增加;当注入粘度较高的水时,由于水的流动性降低,从而使水、油粘度比例随着油的流动性增大而变小。(2)二氧化碳水溶液能与岩石的碳酸盐成分发生反应,并使其溶解,从而提高储集层的渗透率性能,使注入井的吸收能力增强。(3)可降低油水界面的表面张力,从而提高驱油效率。更为重要的是,二氧化碳可促进原油中的轻质烃类(C2～C30)被抽提出来,从而使残余油饱和度明显降低。同时,在不同原油的成分、温度和压力条件下,二氧化碳具有无限制地与原油混相的能力,实际上可以达到很好的驱油目的。二氧化碳在油、水中的扩散系数较高,其扩散作用可使二氧化碳本身重新分配并使相系统平衡状态稳定。注入碳酸水,可大大降低残余油饱和度,因为在含水带内的碳酸水前缘,能形成和保持二氧化碳气游离带。据国外有关资料统计,用二氧化碳驱油若能达到混相状态,油田的最终采收率可达60-70%;若以非混相驱油,油田最终采收率也可达50%以上。广泛的适应性和成本低廉、成效显著、可回收重复利用的特点,使二氧化碳驱油已成为国外三次采油的主要手段。更多还原

【Abstract】 As one kind of oil expellant in improving the recovery ratio for oil reservoir, carbon dioxide has been studied for many years. All the experiments both in laboratories and fields indicate that it is effective oil expellant. Its predominance is shown in the following aspects: First of all, CO2 is apt to be dissolved into crude oil and work in three ways: (1)Make the volume of crude oil increase and enlarge the hole filled with oil, so that feasible condition can be offered for the oil flows. Flowing with the water flooding, amount of the remnant oil would reduce. (2) Reduce the crude oil viscidity and improve its mobility, so that certain oil driving efficiency can be obtained with a small amount of oil expellant. Or in other words, higher driving oil efficiency with certain oil expellant can be got. (3)Improve the sucking function of capillary and expand the scope of oil scanning for the reservoir, so that oil and water flows can be balanced. Secondly, CO2 is apt to be dissolved into water and operate in three aspects: (1)Increase the water viscidity and the mobility of the water is reduced, so that the proportion of water and oil diminishes with the mobility increase of the oil. (2)The carbon dioxide solution can react with the carbonate in the rocks, dissolve the rocks and improve its penetrate capability, so that the absorption ability of the pouring well is strengthened. (3)Decrease the surface intension between oil and water and improve the oil driving efficiency. And carbon dioxide has a good influence on the relative penetrate curves of oil and water, can promote the releasing of light hydrocarbon (C2-C30) from crude oil and make the saturation of oil reduced. Meanwhile under different conditions of compositions, temperatures and pressures of the crude oil, CO2 possesses miscible ability with crude oil limitlessly so driving oil efficiently can be achieved. The high diffusion coefficient of CO2 in oil and water can redistribute itself and make the balanced state of the phase system steady. Pouring into carbonic water can reduce the saturation of the remained oil greatly. Relevant statistics from foreign countries show that the final recovery ratio can be up to 60-70% if CO2 can get the miscibledrive condition. Otherwise the final recovery ratio can be up to more than 50%. The extensive adaptability, low cost, and recoverability have made CO2 become the main way in the third oil extraction in foreign countries.The main part of Caoshe Oil field is netted river sediments of a middle fan. In sandstone quartz is the main composition, with the content of 60-75%; in the gravel, quartz is relatively low, generally in 25-50%, but oddment content is relatively high, the main cementation type is hole pattern, the miscellaneouscontent is 7-15%. Identification in casting slides shows that main cementation material is press connecting pattern hole pattern The main cementation type is hole pattern, and miscellaneous content is7-15%, clay mineral kaolinite is a higher. Drill core determines the hole ratio is 6.3-21.86%, and its average value is 13.21%,penerate ratio is 0.22-342.1 X 10-3nm2, and its average value is 24.77 X 10-3fim2Based on the statistical numeral of testing result, the south-middle to the south-middle faulted block are under identical pressure system, and the temperature field is consistent with a ground temperature grads equation : T=4.9116+3.36 x 10-2H.In the first section of Shutaizhou group, the depth of oil reservoir is 2760~ 3200m, its thickness is 70m, the primitive stratum pressure is 19.29Mpa, stratum temperature is 97.45-108.4℃, and the compress coefficient of the rock and hole is 1.3x10~-4 IV Mpa, its thermal capacity is 2870KJ/ m3 ℃, and heat conduction coefficient is 266 KJ / L ℃, On the up and bottom the thermal capacity and heat conduction coefficient of the rocks are2740KJ / m3 ℃ and 279 KJ / L ℃ =The oil reservoir in Taizhou Group of Caoshe oil field belongs to continent caused crude oil having high content of wax, low sulphurhigh wax and high freezing point, low sulphur, high solidifying point. The density of crude oil on the ground is 0.8310g/cm3, viscidity is about 20.11-106.38mPa.s, and the point of the first distillation is 67-246°C; The density of crude oil in stratum is 0.7534g/cm3, viscidity is 12.83mPa.s, and the determined saturation pressure of the crude oil in stratum is 5.491 Mpa. Reservoir in this area is formed in high-pressure: pressure of pickle pointis 3.94-4.89Mpa, volume coefficient is 1.1319, the scale of gas to oil is 27.96m3/t. Gases in this area are all dissolved gas, and the scale of gas to oil is 24.2m3/t. No. 8 and No 126 well are wells that could be observed with bianshui presently in Caoshe oil field and their water types are mainly composed of Na2SO4, with PH value varies from 6.24-7.99 as well as mineral solubility varies from 4.63-38.53g/cm3. We may make a conclusion that oil produced from these wellsbelong to the typical black oil, after calculating composition of sample through chromatogram analysis, respectively, of 14.252% Cl, 9.411%C2~C6 and 74.277% C7+.Research on the oil reservoir of Caoshe Oil Field regards the reservoir as a thick tabular body. It is isotopic except the differences of the hole degree and penetrate ratio caused by different sediment environments. And this provides the initial mathematical condition at the same time.According to the experiment, the changing rule of the minimal miscible pressure of the oil reservoir in Taizhou group of Caoshe oil field is basically coincidence with MMP Co2-lo =6.05*10"6(1.8T-459.67) ’ 06(C5+) ’78 and we may make a prediction that the minimal miscible pressure of component of the crude oil according to the stratum temperature and composition of crude oil, using the formula stated above if the stratum pressure exceeds the miscible pressure.Depending on stratum volume ratio to represent the multi-phase hydro-mechanical consecutive equation and model, this article has summarized and reasoned mono-phase ^ multi-phase hydro-mechanical consecutive as well as multi-phase transfer equation, which is aimed at solving the problem concerning underground multi-phase hydro-mechanical density.According to the conservation of mass, the black oil mathematic model of "three phases flow" expressed by the volume coefficient of stratum is endued. For adopt a simpler method, the average meaning of " three phases flow " in space-time scale is provided. The entire liquid hydrocarbon and all gaseous phases that appear under the ground condition are regarded as petroleum and gas, only considering their solubility in their concomitancy substances. This make it more significant for the CO2 miscible drives in "three phases".A solid academic foundation concerning the possibility of CO2 expelling oil and simulation before exploration will be established through reasoning model of injecting carbon dioxide within the multi-composition of gas and oil as well as Tri-phase solubility within water, according to the law of energy conservation.A solid theoretical foundation will be established after we first time advancing that CO2 could be utilized in expelling oil under abnormal temperature so as to validate its feasibility.According to the experiment, an accurate standard was utilized in analysis ,dividing crude oil into several parts, respectively including 1.210% N2, 14.282% Cl, 2.292% C2, 1.817% C3, 0.910% IC4, 2.156% NC4, 0.149% IC5, 0.487% NC5, 1.600% C6, 4.597% C7, 7.021% C8, 6.075% C9,5.881%5.881%,and 50.703% C11+. Simultaneity, based on the law of energy conservation, we first time establish a Carbon dioxide expelling oil within multi-composition of oil and gas as well as multi-phase non-isothermal model. This model will establish a firm academic foundation besides its application for the study under non-isothermal condition and play a significant role in studying the dimensional changing rule of saturation, promoting crude oil recovery and offering precise individual pressure data between a series of groups.On the base of non-linear numerical methods of " three -phases" of multi-component, a advanced convergence implicit difference scheme is adopted, also the functional expansion method with finite element method combined is used to compute non-linear model. This creates more conditions for CO2 in modeling the changing law of "great looks".Five main factors including way of carbon dioxide injection, pressure of injection, velocity of injection, total ratio of injection and injection method should be involved when designing plans. However, only the most favorable and practical factors can be selected and combined so as to achieve the goal of efficiency.Using the pouring well net as the foundation, considering the connection and heterogeneous, and because of existing of high influent areas in reservoir of Taizhou group, we must adjust and jam the high influent areas in order to prevent the carbon dioxide from fleeing.The effect of continuous gas pouring and the alternative pouring of gas and water shows that alternative pouring of gas and water can improve the recovery ratio, and when the scale of water and gas is 1:1, the oil volume increase most, so we chose the way of WAG l:lpouring. According to the compare of experience and numerical simulation of Cao3 well, the best result of injection is 0.3HCPV, so we choose it. According to the physical analogy and the analysis of Caoshe, Chujia oil reservoir, the scale should choose 1.0. The long drill core drives always pouring into rate of 0.3PV for the experiment, the best pouring into rate, if the words finishing within 6 years of always pouring into rate of 0.3PV, the pouring into rate is 370RM3/d every day, nearly shut 227t/d. Pouring into the pump is mainly controlled by stratum pressure, stratum absorbability, rubbing hindering and CO2 liquid post pressure. The normal water flooding well head pressure calculates between 23- 24.8Mpa, and the normal gas pouring well head pressure is between 20- 25MPa at present. Because the pressure wellhead can be under 35Mpa, so the normal gas pouring can be guaranteed. Adopt pouring in the way of WAG 1:1, pouring cycle is 90 days, first pouring carbon dioxide for 45 days and then pouring更多还原