This book is conflated based on the last scientific researches by authors and according to the last books and articles which are published in fundamentals of reservoirs engineering. Flow behavior of gascondensate wells stanford earth. Imperial college london department of earth science. It could be argued that the engineering of a gas condensate field is 80% traditional gas engineering, and 20% extra engineering. Often times, it is safe to assume that reservoir fluid behavior is only a function of pressure and independent of composition.
A second case is cycling above dewpoint or depletion of a gas condensate reservoir. At exxon, several fields have been identified in which productivity loss below the dew point has significantly reduced gas recovery by pressure depletion. Condensate reservoirs are inherently more difficult to characterize correctly. Reservoir performance of finegrid models and coarsegrid models was compared using the gascondensate pseudopressure method and showed comparable results in. From pioneering the worlds first timed auto drain valve to offering the most comprehensive range of drain valves and accessories, powerflow is committed to offering its clients the most reliable cost effective condensate management solutions. Except where otherwise noted, content on this site is licensed under a creative commons attributionnoncommercialsharealike 4. In other words, one would expect that gas condensate reservoirs could be treated by a formation volume factor approach with fluid properties determined from laboratory. The liquid dropout curve assumes the two phases remain in contact with one another. Determination of original gas condensate composition in the. This case study investigated the effects of formation reservoir properties, aquifer influx, and production scheme on ultimate recovery and production behaviors of a gascondensate sandstone reservoir sand20 offshore vietnam. Natural gas condensate is a lowboiling mixture of hydrocarbon liquids that are present as gaseous components in the raw natural gas produced from many natural gas fields if the raw gas temperature is reduced to below its hydrocarbon dew point, the liquids begin to condense out of the gas. Gas condensate field produce mostly gas, with some liquid dropout, frequently occurring in the separator.
The percentage of the condensate and liquefiable hydrocarbons ultimately recovered from the reservoir, therefore, is equivalent to the percen tage of the gas recovered, usually 80 to 90 per cent. Interpretation of the unusual fluid distribution in the yufutsu gascondensate field kassem ghorayeb, spe, and abbas firoozabadi, spe, reservoir engineering research inst. It is possible to obtain a sample of the gasconden sate mixture as it exists in the reservoir by lowering a special container down into a well. Pdsview software package for viewing oilfield graphics data files. Depending on the reservoir pressure and temperature and the fluid composition, some gas reservoirs may produce only gas, whereas others produce mostly gas with some condensate. The gascondensate content in gases of various deposits ranges from 12 to 700 cm 3 per 1 m 3 of gas.
Once an accurate model was obtained, the following three solutions to. It is possible to obtain a sample of the gas conden sate mixture as it exists in the reservoir by lowering a special container down into a well. Experimental and simulation constructing of phase diagram. Early developments in reservoir engineering analysis relied on zerodimensional or tank material balances for the evaluation and forecasting of reservoir performance. It is essential to take account of this condensate blockage effect when calculating well productivity. The only liquid associated with the gas from a dry gas reservoir is water. This courseware module is part of penn states college of earth and mineral sciences oer initiative. Gas reservoir management training course petroskills grm.
Much of the pressure drop from condensate blockage occurs within a few feet of the wellbore, where flow rates and capillary numbers are very high. Simulation study of enhanced condensate recovery in a gas. When a gas enters a gas processing plant, always there is a slug catcher unit which the gas passes. The gascondensate content in gases of various deposits ranges from 12 to 700 cm3 per 1 m3 of gas. Approximately 60 well tests have been performed in the gas condensate sections within santa barbara field, and the analysis and interpretation of this data suggests the existence of condensate banking and layered reservoir behavior, as well as well interference effects. Characterization of gas condensate reservoirs using pressure. In a low permeability gas condensate reservoir, the 6 vertical wells have a slightly better performance than the 2 horizontal wells for the same amount of field gas production. Determination of original gas condensate composition in. Calculating well deliverability in gas condensate reservoirs.
The api gravity of 10 is associated with very heavy, almost asphaltic, oils. Compressed air condensate drains archives page 4 of 6. The phase diagram shows the retrograde gas field must have a temperature higher than the critical point temperature. Recovery same as in nonretrograde gas reservoirs under the same conditions and will depend upon. Air reservoirs crvzs technical data function crvzs0. Jasmine, a gas condensate reservoir, is located 240km south east of the coast of aberdeen and is expected to start production at the end of 2012. Condensate becomes immobile when it is below the critical condensate saturation thereby the.
Overall, the reservoir drive indices plot is an important guide for understanding reservoir performance. Mar 30, 2016 reservoir engineering the working tools of the reservoir engineer are subsurface geology, applied mathematics, and the basic laws of physics and chemistry governing the behavior of liquid and vapor phases of crude oil, natural gas, and water in reservoir rock. The need for integration had been recognized earlier particularly for gas condensate reservoir, gas cycling processes, and volatile oil systems. Pdf gas condensate pseudopressure in layered reservoirs. However, when the bottomhole flowing pressure is less than the saturation pressure of the original reservoir oil, gas escapes from the oil around the wellbore and is produced.
Reservoirs with the relative amount of at least 5 to 10 grams of condensate per cubic meter are. In addition, for very rich gas condensate, the condensed oil will flow in the reservoir when the oil saturation is higher than the critical oil saturation. Pdf understanding the behaviors of gas condensate reservoirs. In addition, a twophase region exists between the bubble point and dew point lines. At discovery, these reservoirs are often in single phase. Several examples of severe productivity decline are available in the literature. Modeling gas condensate reservoir fluid systems with an equation of state is discussed, as is eos modeling of complex fluid systems with strongly varying compositions and pvt properties. For denser gas condensate fluids in geopressure systems, the behavior of b g with pressure is a critical indicator of our ability to obtain solutions within reasonable bounds with analytical mb. The vertical line on the phase diagram shows the phase changes in. A phase diagram is illustrated in the next picture. To forecast hydrocarbon production, the original fluid composition and condensate blockage has to be determined.
Compositional modeling of gascondensate reservoirs. Evaluation of gas condensate reservoir behavior using. This case study investigated the effects of formation reservoir properties, aquifer influx, and production scheme on ultimate recovery and production behaviors of a gas condensate sandstone reservoir sand20 offshore vietnam. A case study of gascondensate reservoir performance under. Gas condensate reservoirs are the categories of hydrocarbon reservoirs.
Reservoir that yield natural gas can be classified into essential four categories, these are. Interpretation of the unusual fluid distribution in the. Stanley kleinsteiber is a senior petroleum engineer with mha petroleum consultants inc. The literature shows many differences between gas condensate reservoirs and dry gas reservoirsi6. One question often asked is during and after sampling. Spe, iniercomp resource development ana engineering, inc. Tlv, 20153 the flashing of condensate under reduced pressure as it moves from the conditions of on effect. Condensatetogas ratio cgr plays a significant role in sales potential assessment of both gas and liquid, design of the required surface processing facilities, reservoir characterization and modeling in gascondensate reservoirs. The first step of the study involved gathering north field reservoir data from previously published papers. As the pioneering world leader in for almost 40 years powerflow electronics have been at the forefront of compressed air condensate management. In other words, one would expect that gascondensate reservoirs could be treated by a formation volume factor approach with fluid properties determined from laboratory. Engineer your gascondensate systems, reservoir to sales meter shah kabir chevron energy technology company spe 95531, 95528, 89753, 89754, 100384.
Gas condensate reservoirs usually exhibit complex flow behaviors due to the buildup of condensate banks around the wells when the bottomhole pressure drops below the dew point. This case is described in detail in the following sections. Lean gas condensateleanlean gas condensate gas condensate rich gas condensaterichrich gas condensate gas condensate 0 0. A gas condensate with low condensate formation in the reservoir. Reservoir engineers have been concerned about the impact of condensate blocking on productivity for many years. In case of isothermal reduction of the formation pressure, part of them condenses in the form of gas condensate. Phase behavior is relevant to every aspect of petroleum and natural gas engineering. Simulation study of enhanced condensate recovery in a gascondensate reservoir iranian journal of chemical engineering, vol.
The technique requires that a well be produced for a period of time and then shutin for an appropriate length of time. Natural gas condensate encyclopedia article citizendium. The rich gas drops out more condensate than the lean gas bottom leftt. 95 16 bar the reservoirs can be used to compensate pressure fluctuations, and act as accumulators in the event of sudden air consumption they can also be used to provide. Kleinsteiber has over 24 years of petroleum engineering experience and has authored or coauthored papers dealing with production decline type curve analysis, co2 flooding, and depletion of a rich gas condensate reservoir by. It is reasonable to assume, therefore, that reservoir fluids on the other side of the critical point e. However, depicting phase diagrams to show phase behaviour, with correspondent quality lines for very high lean gas condensate reservoir. Reservoir performance of finegrid models and coarsegrid models was compared using the gas condensate pseudopressure method and showed comparable results in all cases studied, including relative. Reservoir pressure of condensate gas reservoir is an indispensable parameter for calculation of gas reserves, gas well productivity evaluation, dynamic analysis, and evaluation of anticondensate. Gascondensate reservoir article about gascondensate. Slug catcher is used at the terminus of offshore pipelines to catch large slugs of liquid in pipelines, to hold these slugs temporarily, and then to allow them to follow into downstream equipment and. Overall, the reservoirdrive indices plot is an important guide for understanding reservoir performance. Hydrocarbon liquid dissolved in saturated natural gas that comes out of solution when the pressure drops below the dewpoint.
From the tank the condensate is pumped into the feedwater tank by a levelcontrolled pump, in most cases via a deaerator. According to the previous studies, the addition of some nitrogen causes a considerable increase in mixture dew. Michael adewumi, vice provost for global program, professor of petroleum and natural gas engineering, the pennsylvania state university. Simulation study of enhanced condensate recovery in a gas condensate reservoir iranian journal of chemical engineering, vol. According to the complexity of the reservoir fluid phase behavior, reservoir modeling is classified under two distinct groups. In all cases their compositions depend upon their source, history, and present thermodynamic conditions. Engineer your gas condensate systems, reservoir to sales meter shah kabir chevron energy technology company spe 95531, 95528, 89753, 89754, 100384. This means the richer in condensate, the more liquid drops out of the gas in the reservoir. Summary this paper presents a generalized equation of state eos that represents several widely used cubic eoss.
Oct 11, 2017 the percentage of the condensate and liquefiable hydrocarbons ultimately recovered from the reservoir, therefore, is equivalent to the percen tage of the gas recovered, usually 80 to 90 per cent. Condensate recovery and return system quick cc application condensate tanks are used to collect the condensate coming from steam users or flash vessels. Production with gor 100,000 scfbbl is commonly called lean or dry gas. Spe 109892 lbc viscosity modeling of gas condensate to. For denser gascondensate fluids in geopressure systems, the behavior of b g with pressure is a critical indicator of our ability to obtain solutions within reasonable bounds with analytical mb. Jasmine, a gascondensate reservoir, is located 240km south east of the coast of aberdeen and is expected to start production at the end of 2012. The phase behaviour of gas condensate mixtures has been extensively studied and reported in literature 4,7. Characterization of gas condensate reservoirs using. Under natural conditions, a gas condensate is a solution of heavier hydrocarbons. The greater drop in pressure around the wellbore extends. When pressure decreases at reservoir temperature, a rich gas top leftt forms a higher percentage of liquid than a lean gas top rightt. Nodoc estimate and simulate the cost for the remoavl of condensate and water from gas. With the introduction of pressurederivative analysis and the development of complex interpretation models that are able to account for detailed geological features, well test analysis has become a very powerful tool for reservoir characterization. Fundamentals of gas reservoir engineering, volume 23 1st.
Gas condensate is one of the most different fluids in reservoir simulation due to retrograde condensation in case of pressure reduction. Figure 1 provides a fairly typical gor versus total flow rate response from a gas condensate reservoir. Gas condensate banking application of pressure transient. The gas condensate separated from natural gas at reduced pressure andor temperature by reverse condensation is a colorless or slightly colored liquid of density 700800 kgm 3, which begins to boil at 3070c. A commercial simulator was then used to carry out numerical reservoir simulation of fluid flow in the north field. Simulation of gas condensate reservoir performance keith h. Optimum production strategy was then formulated to maximize the hydrocarbon recovery while reducing the water treatment cost.
Reservoir engineering the working tools of the reservoir engineer are subsurface geology, applied mathematics, and the basic laws of physics and chemistry governing the behavior of liquid and vapor phases of crude oil, natural gas, and water in reservoir rock. For the example field investigated here, numerical simulation of pressure transient behavior was also used to validate the initial condensate gas ratio and relative permeabilities. Pdf application of general material balance on gas. Gas condensate fields is a single subsurface accumulation of gaseous hydrocarbons including gasoline and kerosene vapors and, less frequently, components with a higher molecular weight. On the contrary, the performance of the 2 horizontal wells in a tight gas condensate reservoir is superior to that of the 6. Well test analysis has been used for many years to assess well condition and obtain reservoir parameters. Oil and gas reservoir engineering linkedin slideshare. In this kind of fluids, two phenomena named negative inertia and positive coupling, become significant in the high velocity zone around the wellbore. The effect of trapped critical fluid saturations on. Gas reservoir engineering spe textbook series lee, w. Natural gas condensate article about natural gas condensate.
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