| 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. |
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