【作者】 黄郑；

【导师】 姚光庆；

【作者基本信息】 中国地质大学 ， 油气田开发工程， 2014， 博士

【摘要】 凝析气田在世界气田开发中占有重要的地位。高效开发凝析油气藏的中心问题是优选出最佳的开发方式,通常情况下大型的高含凝析油的产出气藏和无足够外销市场的饱和凝析气藏适合循环注气开发,小型的低凝析油含量的高地露压差的凝析气藏适合衰竭式开发。而低渗、中—高凝析油含量的小型饱和凝析气藏开发方式的选择一直以来是凝析气藏开发的难点。本文以宝浪油田宝中凝析气藏为例,以室内实验成果为基础,判别宝中凝析气藏类型,分析相态特征、反凝析特点、凝析油临界流动饱和度；以单井及井组测试、生产资料为基础,对循环注气先导试验井组进行了评价；建立了三维地质模型和三维数值模型;运用公式法、类比法、数值模拟等方法开展凝析气藏工程研究；采用数值模拟方法对不同开发方式下开发效果进行预测,评价宝中凝析气藏循环注气可行性。通过本项目研究,方面为下一步高效开发宝中区块凝析气藏提供科学依据；另一方面对国内外同类型油气藏高效开发具有参考和借鉴作用。本论文研究取得的研究成果和主要认识可以概括为以下几个方面：利用四参数判别法、含气系数与C2+含量关系判别法、地层流体密度和平均分子量判别法、φ1参数判别法、地面生产气油比和油罐油密度判别法、储层流体三原组成三角图判别法、凝析气藏是否带油环判别方法,综合判断宝中凝析气藏属带油环的凝析气藏。焉参1井与宝中201井样品代表性较好,从实验分析井流物构成看,不同井流体组成十分相近,甲烷加氮气(C1+N2)含量为71.11-71.65%；乙烷到已烷加二氧化碳(C2～C6+CO2)含量为23.98～24.77%;庚烷以上(C7+)含量为3.59～4.91%,总体上可以看出该区流体组分构成变化不大宝中凝析气藏在不同层位、不同构造部位的样品具有相同的相态特征,即地层压力几乎等于露点压力。焉参1井地层压力为28.16MPa,露点压力为26.95MPa；B201井地层压力为27.94MPa,露点压力27.94MPa。凝析气相图露点线包络区域较大。从气藏反凝析特点看,反凝析现象比较强烈。早期取样最大反凝析饱和度为13.95%(19.86MPa),而新测试的饱和凝析气最大反凝析饱和度为15.38%(15MPa)。宝201井反凝析液量随衰竭压力的降低起初有一个快速上升的趋势,之后速度有所减缓。CVD过程随着衰竭压力的降低,采出井流物越来越轻。在废弃压力6MPa和原始地层压力27.94MPa时,凝析气藏天然气的采收率为80.09%,凝析油的采收率为20.41%。经气顶与油环相平衡判断,可知目前气顶与油环基本处于平衡。通过对比,宝201井闪蒸到宝3井地层条件下所得到平衡油与宝3井原油特征相近,说明油环与凝析气顶性质是匹配的,宝中201井为饱和的带油环的凝析气藏。用电解式水含量分析仪直接测定天然气中的含水量,在原始地层压力为27.94MPa时,地层凝析气饱和含水量的实验值为1.4614g/m3,现场试气结果表明,现场气水比生产值均大于26g/m3,远高于实验测试饱和含水气量,这说明宝201井地层凝析气中含水量已达到饱和,地层中存在游离水。对凝析油的临界流动饱和度进行了探索性研究,利用超声波装置通过长岩心衰竭实验测试了长岩心中凝析油的临界流动饱和度为8.01%,相应的临界流动压力为17.70MPa。在实验温度为地层温度(106.6℃)和实验压力为原始地层压力(27.94MPa)的条件下进行了长岩心中凝析气衰竭实验。长岩心中凝析油采收率为34.40%,比PVT中凝析油采收率高13.99%。凝析气衰竭的天然气的采收率和PVT筒中定容衰竭的采收率相差不大。多孔介质对凝析气相态的影响非常复杂,目前还未形成较为统一的观点。在多孔介质CVD过程中,当凝析油饱和度达到临界流动饱和度时会流动,一般凝析油采收率均比PVT测试中的要高。结合钻井、分层、断层、构造等基础资料,利用Petrel建模软件,建立了宝中凝析气藏的构造、沉积相、岩性、物性、净毛比和含油饱和度等三维定量化模型。通过计算模型储量,各层储量相对误差小于5%,说明所建地质模型较为准确,模型真实可靠。根据地质建模成果,利用Eclipse建模软件,结合PVT相态拟合、压力、系统、油气水界面等,建立了宝中凝析气藏三维数值模型。通过拟合气井的日产气、日产油、流压和静压数据,对比气井开发生产历史数据,与生产实际符合率较高。根据早期宝中凝析气藏循环注气试验井组方案地层吸气能力研究结果,宝2612井Ⅳ油组井口注气压力大于28MPa才能注进气,日注气量为2×104m3/d。循环注气先导试验井组实施后,实际井口注气压力21MPa就可以吸气,日注气量达11×104m3/d左右,并一直稳定在22MPa左右,注气能力好于先导试验井组方案预期。从循环注气试验井组单井以及井组整体看,循环注气阶段井组注采基本平衡,凝析油气产量基本稳定,产量递减幅度明显放缓,气油比有所上升,但上升幅度不大,注气后采气井油压下降率和套压下降率均发生了明显的减小,循环注气效果显现。从循环注气试验井组三口生产井原油化合物含量变化情况看,三口井原油中的C3-C7化合物含量升高,而Cs-C32化合物含量降低,说明轻烃含量增加,重烃含量减少,循环注气效果已经显现。从宝201井2011年的试井解释成果与2006年的解释成果相比,渗透率由注气前0.2419mD上升到0.499mD,表皮系数由注气前16.27下降到11.6。说明循环注气疏通储层孔道,反凝析污染有所降低,使得储层物性变好。利用RTA方法、简易物质平衡法和宝中凝析气藏历年测压情况,综合评价试验井组地层平均压力约19.5MPa。说明循环注气时间短,地层亏空较大,目前压力保持水平70%。使用压力判断法、气油比变化率判断法、干气波及系数判断法3种气窜判断方法评价,认为宝中凝析气藏未发生气窜现象,通过循环注气试验井组受效情况和气窜情况来看,初步判断目前注采井距是合理的。从循环注气试验井组三口生产井实际生产资料来看,凝析气藏实际产能要高于试井时的结果,对气井的产能进行了修正。重新修正产能后,宝2325井Ⅳ油组无阻流量为9.5×104m3/d;宝201井当Ⅲ油组单采时,无阻流量为4.35×104m3/d, Ⅲ、Ⅳ油组合采时无阻流量为8.38×104m3/d, Ⅱ、Ⅲ、Ⅳ油组合采时气井无阻流量为11.63×104m3/d；根据JOSHI水平井产能公式及参数,宝气平1井Ⅳ4层无阻流量为20.6×104m3/d。根据修正后的气井产能方程分别对循环注气试验井组直井和水平井合理产量进行了评价。宝201、宝2325井在合理生产压差8.0MPa条件下合理产量分别为2.7×104m3/d、4.1×104m3/d,平均3.4×104m3/d；宝气平1井在合理生产压差4.0MPa下,合理产量为5.5×104m3/d。通过计算B201与B2325两口试采井的油套压与计算的携液临界产量,这两口井的携水临界产量分别为：1.7与1.4-1.7×104m3/d,携油临界产量分别为：0.8与0.7-0.8×104m3/d。油管尺寸越小,气井越容易携液,因此可以在气井开采中后期,采用优选小油管的方式,实行带液生产。依据循环注气先导试验注气情况,对宝2612产能二项式方程进行了改进,采用节点分析法对不同地层压力、不同产气量下气井井底流压进行计算。当注入气量为11×108m3/d,地层压力为22MPa时,井底流压约为29MPa,评价结果与现场基本相符。通过类比法、单井控制经济极限储量法、规定单井产能法、数值模拟法(单井典型模型),结合循环注气试验井组实际见效与气窜情况,综合评价宝中凝析气藏合理井距为450-600m。利用经验法,宝中凝析气藏衰竭式开采的合理采气速度应为5%,利用数值模拟法结合实际生产情况,采气速度越大,凝析油采出程度越大,效益越好；但是采气速度过大,会使气井递减过快,当采气速度大于4%后,气井注采不平衡。因此,推荐循环注气采气速保持在3.5-4%左右为宜。采用类比法、地层不发生明显反凝析压力界限法、储层结构不被破坏压力界限法、节点分析法结合实际生产压差,综合评价宝中凝析气藏直井合理生产压差约为8MPa。注气时机对凝析油采收率影响很大。利用数值模拟,设计了5个方案,早期注气(生产即注气)、生产1年后注气、生产2年后注气、生产3年后注气、生产4年后注气,与不注气进行了对比。采用早期注气,凝析采出程度增加最大,而当4年后再注气,凝析油采出程度增加只有早期注气的一半,所以越早注气对凝析油采收率提高越明显。循环注气时间越长,循环周期内提高凝析油采出程度越大。但是,随着循环注气时间的增加,单位注气量所增加的凝析油量减小,对于宝中凝析气田循环注气方案注气时间推荐8-11年为宜。利用三维数值模拟对不同注采比方案进行预测表明,提高注采比可以提高凝析油的采出程度。但是注采比也不是越高越好,注采比越高,越容易造成气井气窜,循环注气效果反而变差。同时由于地方天然气需求强烈,无外来干气补充,因此,宝中凝析气藏的注采比推荐0.95-1。采用类比法、经验公式法、气藏埋深计算法、以经济—产能方程法对宝中凝析气藏废弃地层压力进行了评价。综合确定宝中凝析气藏的废弃地层压力为10.2MPa。采用类比法、经验公式法、定容衰竭试验法、数值模拟法对宝中凝析气藏采收率进行了综合评价。综合评价凝析气藏天然气采收率为60%,衰竭开发凝析油采收率约为24%,循环注气开发凝析油采收率约为40%。循环注气先导试验井组Ⅳ油组的开发效果要好于方案预期,与Ⅲ油组和Ⅳ油组合采相比,分层系开发,能最大限度提高注入效率,增大主力层位的凝析油采出程度。推荐Ⅲ、Ⅳ油组分层系开发。以目前已部署井网为基础,对宝中凝析气藏以不同开发方式设计了4套整体开发方案。由4个方案的开发指标可以看出：①方案1(衰竭式开采)虽然初期日产油量高,但是产量递减快,方案2(Ⅲ、Ⅳ油组循环注气开发)虽然初期日产油量低,但是产量递减慢；②累计产油量从高往低的是,方案2(Ⅲ、Ⅳ油组循环注气开发)、方案4(Ⅳ油组循环注气开发,Ⅱ、Ⅲ油组衰竭式开采)、方案3(Ⅳ油组循环注气开发,Ⅲ油组衰竭式开采)、方案1(衰竭式开采)。方案2凝析油累积产油量可达56.6×104m3,方案1凝析油累积产油量只有31.7×104m3,方案2比方案1多产24.9×104m3；③凝析油采出程度从高往低的是,方案2、方案3、方案4、方案1,方案2比方案1高17.5%；④天然气采出程度从高往低的是,方案2、方案3、方案4、方案1,方案2比方案1高9.3%;⑤经济评价结果从高往低的是方案2、方案4、方案3、方案1。从日产油量、累计产油量、凝析油采出程度、天然气采出程度、经济评价指标看,Ⅲ、Ⅳ油组循环注气开发的方案2,全面大幅度优于衰竭式开采的方案1,部分循环注气,部分衰竭式开采的方案3、4也都优于衰竭式开采的方案1。循环注气开发,可以大大提高宝中凝析气藏的凝析油的采出程度。因此,从技术上、经济上看,宝中区块这类低渗透小型高含凝析油的饱和凝析气藏循环注气开发是可行的。更多还原

【Abstract】 The condensate gas fields hold special and important position in the development of the world gas fields. The efficient development of the condensate gas fields was always a world problem. Optimizing the situable way to develop palys an essentical role in the exploiting condensate gas fields, especially for small saturated condensate gas reservoirs with low permeability and mid-high condensate oil content. In this thesis, the condensate gas reservoirs of Baolang oil field was selected as an example, based on the experiment results, throughing the analyse of the phase equilibrium theory and the theory of phase recovery, the condensate gas reservoir fluid phase state diagram was build, by which, the characteristics of the gas cap and oil ring were concluded and the types of the condensate gas phase were decided. Based on the experiment and production datum, with the result of cyclic gas injection experiment, the gas reservoir engineering research, such as identifying the production, both liquid critical production, and note well injectivity was developed by the useage of Formula method, analogy method, experience method. The speed of depletion development and the development of cyclic gas injection wells, reasonable drawdown pressure, abandonment pressure and recovery factor were also decided. After that, the numerical simulation method was used to predict the development effect of different ways, the development index and economic index can be compared, and the condensate gas reservoir feasibility of cycle gas injection can be evaluated. In this paper the research achievements of research and the main knowledge can be summarized as the following aspects.The condensate gas reservoir of Baozhong area was belonged to the reservoirs of oil ring, which can be judged by the methods of four parameters, gas coefficient relationship with C2+content, formation fluid density and average molecular weight,(?)1parameters, the ground production gas oil ratios and the density of oil tank, the reservoir fluid of triangle. From the experimental datum of two wells, the fluid composition of the different Wells and formation were the same, the composition of the C1&N2was71.11%to71.65%, the composition of the C2～C6&CO2was23.98%to24.77%, the composition of the C7+was3.59%to4.91%. The samples from Yancanl and Baozhong201were Representative, by which the vertical and horizon change trend of the can be reflected precisely. On the whole, it can be seen that the fluid component composition nearly same.The samples of the different formations and tectonic positions had the same Phase behavior characteristics, so the pressure of formation is equal to the pressure of water. The pressure of Yancan1was28.16MPa, the pressure of water is26.95MPa, the pressure of B201was27.94MPa, the pressure of water was27.94MPa. The dew point of condensate gas phase diagram line envelope area was larger.From the characteristics of the retrograde condensation, the experiment results of the samples present a phenomenon of retrograde condensation. The early experiment sample result was13.95%(19.86MPa), while the later was15.38%(15MPa).The amount of retrograde condensate fluid of B201rose rapidly at the primary stage of the pressure falling, and then the rising speed declined. When the pressure drop to15MPa, the amount reached the peak (15.38%), after that the mount reduced gradually. In this period, the production well flow more and more light. When the abandonment pressure was under6MPa, the original formation pressure was27.94MPa, the recovery of the gas was80.09%, and the oil was20.41%.The gas cap and oil ring in the basic were on balance. The characteristics, Single degassed oil ratio, viscosity and density of the oil of B201and B3were identical. Comprehensive consideration can be thought that Oil ring and the nature of the condensate gas cap is matching, well B201is condensate gas reservoirs with oil ring.The water content of the gas was decided by the electrolytic water analyzer, when the origin pressure was27.94MPa, formation of condensate gas saturated water content was1.4614g/cm3, the field test results show that the gas and water output index was more than26g/m3, which show that the water content of the condensate gas of well B201has saturated and the free water exited in the formation.Through the long core depletion experiment, the critical flow saturation of oil condensate in the long cores is tested by the use of ultrasonic device, which is8.01%with the corresponding critical flow pressure17.70MPa.The values of the gas recovery of the failure gas condensate in the long cores and the recovery of constant volume depletion in the PVT cylinder are more or less the same. However, the value of the gas recovery of the failure oil condensate in the long cores is higher than the value of the recovery of constant volume depletion in the PVT cylinder. The recovery of the oil condensate in the long cores is34.40%, and it’s13.99%higher than the oil condensate recovery in PVT cylinder.Based on the integrated data processing, the comprehensive study of sedimentary facies analysis and the extensive manual mapping, the three-dimensional quantitative models are established, including structure, sedimentary facies, litho logy, physical properties, net gross ratio and oil saturation of the gas condensate reservoirs in Baozhong. By calculating the model reserves, the relative error between reserves the layers is less than5%, indicating that the geological model is more accurate, model reliable.According to geological modeling results, combination with the PVT phase fitting, pressure, systems, oil-water interface etc, the three-dimensional numerical simulation model of the gas condensate reservoir is built. In the procession of calculating reserves, fitted the II, III, IV oil group, the relative error of natural gas reserves is0.24%and the relative error of condensate reserves is4.3%, and tested the rationality of the static parameters in the model. By fitting the daily gas production, daily oil production, flowing pressure and static pressure data of the gas wells, compared with the historical data of development and production of the gas wells and the calculated index, it’s in line with the actual production of the higher rate.As of30June2013on the6th, the Baozhong gas condensate reservoir1Note3mining cycle gas injection test well group, the cumulative gas production is2.35×108m3, the cumulative oil production5.88×104m3, and the cumulative gas injection0.68×108m3in the injection test area. So far, the average daily gas production is9.4×104m3, the average daily oil production19.3m3, and daily gas injection10.7×104m3.According to the stratigraphic inspiratory capacity findings of " the cycle gas injection test well group plan of the Baozhong gas condensate reservoirs", when the wellhead injection pressure of the IV oil group in B2612oil well is greater than28MPa, it can inject air intake, and the daily injection volume is2×104m3/d. However, when the actual wellhead injection pressure is21MPa, it can inhale. And the daily gas injection capacity is11×104m3/d or so, and has been stable at around22MPa. The ability of gas injection is better than the expectations of tested well group program.From the respects of cycle gas injection test wells in the single well and the well groups in whole, the well group injection in the cyclic gas injection stage was basically balanced, the production of gas condensate was stable, the decline rates of production were significantly slowed, the gas-oil ratio has increased, but the rise was little. After gas injection, the decline rates of oil pressure and the casing pressure occurred significantly reduced, and the cycle gas injection has yielded good results.From the changes of the compounds in crude oil of the three production wells in the cycle gas injection test wells group, the C3-C7compounds contents in the crude oil of the three wells increased, while the Cs-C32compounds contents decreased. It indicated that light hydrocarbons contents increased, heavy hydrocarbons reduced, and the cyclic gas injection has yielded good results.By use of RTA method, simple material balance method and the manometry cases of the Baozhong gas condensate reservoir over the past years, the comprehensive evaluation of the current formation pressure of B201well, B2325well, Bao Ping1gas well and Bao2612well is studied. The results were18.2MPa,18.4MPa,19.8MPa,21.7MPa respectively, and the average of well group is about19.5MPa. Indicated that the gas injection cycle time is short, the formations deficit is larger, and the current pressure maintained to the level70%.Using the pressure judgment method, the gas-oil ratio to determine the rate of change method and the dry gas sweep efficiency judgment method those three kinds of judging gas channeling methods to evaluate. And determine that the Baozhong gas condensate reservoirs did not occur the gas channeling phenomenon. Through the cycle gas injection wells set by the efficiency of the test case and the gas channeling situation, the initial determination that the current injector spacing is reasonable.From the current actual production point of view, the actual results of the gas condensate reservoir production capacity is higher than the results of the well testing. So there is the need to correct the well productivity, and re-evaluate its production capacity. The unimpeded flow of the IV oil group of the B2325well is9.5×104m3/d. In B201oil well, when the oil group III aphaeresis, the unimpeded flow is4.35×104m3/d; while Ⅲ, IV oil groups combinations mining, the unimpeded flow is8.38×104m3/d; while Ⅱ,Ⅲ,Ⅳ oil groups combinations mining, the unimpeded flow is11.63×104m3/d. According to the JOSHI horizontal well productivity formula and parameters, evaluated the unimpeded flow of Bao Ping1gas well is20.6×104m3/d.According to the well productivity equation, evaluate the reasonable yields of the straight and horizontal wells in the injection test area respectively. Analysis showed that in the area the vertical wells B201, B2325under the reasonable conditions of pressure8.0MPa produce the reasonable yields were2.7×104m3/d,4.1×104m3/d, the average is3.4×104m3/d; Bao Ping1gas well at the reasonable level production pressure of4.0MPa, the reasonable yield is5.5x104m3/d.By calculating the oil casing pressure and the carrying liquid critical production of the two testing wells B201and B2325, the current carrying water critical production were1.7and1.4-1.7x104m3/d respectively, the carrying oil critical production were0.8and0.7～0.8×104m3/d respectively. The smaller of the tubing size, it’s easier to carry liquid in gas wells. So we can use the way of preferred small tubing to implement with liquid production in the gas wells in exploration of the middle and late stage.Based on the gas injection situation of the Pilot experiment of cyclic gas injection, the Binomial equation of the capacity of B2612was improved, in the situation of different pressure and gas production, the flowing pressure of the bottom of the wells were calculated. When the injection volume was11×108m3/d and the pressure was22MPa, the flowing pressure of the bottom was about29MPa, the evaluation result was equal to the reality.Through the method of analogy and compared with the condensate gas reservoirs of Yakela and Dalaoba, the reasonable distance of wells of Baozhong condensate gas reservoir was680-950m, through the method of economic limit reserves of the wells, the distance of wells is500m, through the capacity method, the distance of wells is580m, through the method of numerical simulation, the distance is500-700m. Composed of the effect of the wells of cycling test, the distance of wells is450-600m.Through the method of experience and economic evolution, the price of gas and oil was 1.0￥/m3and3000￥/t, so if the Condensate gas reservoir was recovered with the Failure type, the reasonable gas recovery rate was3.8～4.8%, which can continue3.8-4.7years. Through the method of numerical simulation and combined with the actual production situation, if the recovery rate increased, the recovery rate was more high and the effect was better, but the mount deduced more, when the rate was more than4%, the injection and the recovery was not on the balance. So the rate was appropriate to keep3.5-4%. Through the method of analogy, not occurring of the obviously retrograde condensation pressure boundary strata, non-damaged of the reservoir structure, the node analysis and composed of the statistical of the practical production, the available differential pressure is about8MPa.The gas injection timing made importance on the condensate oil recovery. When the injection was earlier, the largest condensate recovery degree increased, while it is injected after4years, the degree only was the half. So the earlier the gas was injected, the larger condensate recovery degree increased. After all, the injection time of Baozhong gas condensate field was8-11years.Through the method of3D numerical simulation to predict the different injection-production ratio, improving the Injection-production ratio can improve the recovery degree of condensate oil. But the effect was no better with the higher ratio, when the ration increased, the gas was easy to move and the effect of cyclic gas injection vitiated. Because of the strong need of the gas but without other gas to supply, the ratio was better0.95-1.By the method of analogy, empirical formula, constant volume failure test and the numerical simulation, the recovery of the condensate gas reservoir was evaluated. The recovery rate of the gas was60%, the oil recovery rate of failure and cycling were24%and40%respectively.The results of plan1-4are predicted twenty years from now as follows.1) The effect of cyclic gas injection is obvious. Compared with depletion-drive development, the degrees of reserve recovery in plan2,3and4is higher at the end of cyclic gas injection and twenty years from now, the extra percentages of condensate oil and natural gas in which are up to8.9-17.5and4.9-9.2respectively.2) The degrees of reserve recovery of condensate oil in plan3is less up to6.5%than that in plan2, due to depletion-drive development in oil group Ⅲ.3) The cumulative gas production and cumulative oil production in plan4both improve due to extra development of oil group II, but the degree of reserve recovery of condensate oil in combined oil group Ⅱ,Ⅲ and Ⅳ is lower twenty years from now due to the depletion-drive development in oil group Ⅱ.更多还原