These traps are capable of removing up to 2800 pounds of condensate per hour and work with pressure differentials from 5. Summary this paper presents a generalized equation of state eos that represents several widely used cubic eoss. Wet gas, condensate and natural gas liquids are all synonyms. The first step of the study involved gathering north field reservoir data from previously published papers.
The vertical line on the phase diagram shows the phase changes in. Evaluation of gas condensate reservoir behavior using. The condensate is not only generated into the reservoir, it is also formed when liquid drops out, or condenses, from a gas stream in pipelines or surface facilities. 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. A further complication of this problem is that the composition of the surface liquid also changes. Appendix b includes some special physical and mathematical constants that are of particular interest in gas reservoir engineering. Simulation study of enhanced condensate recovery in a gas. This video is considered as an educational video used for nonprofitable purpose for all petroleum and nonpetroleum students in bue the british university. Composition variation during flow of gascondensate wells. Gascondensate reservoir article about gascondensate. As shown in figure 11, gas condensate reservoirs are defined as reservoirs that. This paper will attempt to explain when and why various pvt properties are important to the development of a particular gas condensate field.
Compositional modeling of gascondensate reservoirs. For compositionallygrading reservoirs with a transition from gas to oil through an. It is called retrograde because some of the gas condenses into a liquid under isothermal conditions instead of expanding or vaporizing when pressure is decreased. Stanley kleinsteiber is a senior petroleum engineer with mha petroleum consultants inc. According to the previous studies, the addition of some nitrogen causes a considerable increase in mixture dew.
Us3149668a us858752a us85875259a us3149668a us 3149668 a us3149668 a us 3149668a us 858752 a us858752 a us 858752a us 85875259 a us85875259 a us 85875259a us 3149668 a us3149668 a us 3149668a authority us united states prior art keywords gas reservoir water dry gas injection prior art date 19591210 legal status the legal status is an. Gas reservoirs lend themselves to easy calculation of the hydrocarboninplace through a general gas law equation. The feasibility of different methods such as periodic hot gas injection and gas reinjection using horizontal wells were assessed using different reservoir fluid and injection conditions. Pressure decline below the dew point pressure causes condensation to occur which creates a hydrocarbon liquid saturation in the reservoir. Calculate the number of poundmoles in gas by dividing the gascondensate ratio gas volume in cubic feet per barrel of condensate by 379. As is shown in table 1, the content of intermediate hydrocarbon components is about 25. Simulation study of enhanced condensate recovery in a gascondensate reservoir iranian journal of chemical engineering, vol.
A dry gas reservoir is defined as producing a single composition of gas that is constant in the reservoir, wellbore, and leaseseparation equipment throughout the life of a field. The depletion of rich, gas condensate reservoirs to pressures significantly below the dew point is a topic of increasing interest as deeper, hotter hydrocarbon reservoirs are exploited. The gas may be in the gaseous phase at liquid reservoir conditions but may condense to form some liquid at some point in the. Calculating well deliverability in gas condensate reservoirs. Operations in the outer continental shelf general performance standards 250. Modeling a rich gas condensate reservoir with composition grading and faults. A case study of gascondensate reservoir performance under. Applied petroleum reservoir engineering 3rd edition.
Following success at the main objective, the well was deepened to a final depth of 3633 m. Gas condensates are hydrocarbons in which conditions of temperature and. The cost and risk to develop reservoirs under these extreme conditions highlights the need to be able to confidently predict the recovery of gas and liquids. Condensate as a mixture consisting primarily of hydrocarbons heavier than pentanes that is recovered as a liquid from natural gas in lease separation facilities. Under natural conditions, a gas condensate is a solution of heavier hydrocarbons. If the original reservoir pressure is greater than the dewpoint pressure, then a singlephase gas system will occur in the reservoir as in figure 2.
Sand20, the target reservoir of this study, is a relatively homogeneous and isotropic sandstone reservoir with thickness of approximately 100 ft and horizontal permeability on. In certain cases, the assumption of fixed oil and gas composition is no longer valid. Natural gas condensate aka gas condensate, condensate, natural gas liquids is a lowdensity, highapi gravity liquid hydrocarbon phase that generally occurs in association with natural gas. Equation 3 shows that the well production rate is directly dependent on krg in region 1. Condensate recovery factor is characteristic of the degree of recovering gas condensate from gas condensate and oilgas condensate fields. Gas condensate reservoir, history matching, simulator.
Hence the key parameter in determining condensate blockage is the relationship. The particles are coated with the liquid phase to give a large surface area for dissolving the gas. This category excludes natural gas plant liquids, such as butane and propane, which are recovered at downstream natural gas processing plants or facilities. Reservoir simulation models are commonly used to predict the performance of retrograde gascondensate reservoirs. Based on known moles of gas and condensate, determine the fraction of produced gas and condensate in the reservoir fluid stream. Condensate reservoirs are inherently more difficult to characterize correctly. Appendix a lists the commonly used units in gas reservoir engineering, along with their conversion factors. Compositional modeling of gascondensate reservoirsthe. Reservoirs with the relative amount of at least 5 to 10 grams of condensate per. Condensate blockage study in gas condensate reservoir.
Gas reservoir management training course petroskills grm. In this chapter, gas reservoirs have been divided into three groups. Optimum production strategy was then formulated to maximize the hydrocarbon recovery while reducing the water treatment cost. Gas condensate reservoirs are the categories of hydrocarbon reservoirs. This reduces the relative permeability and therefore gas production. Engineer your gascondensate systems, reservoir to sales meter shah kabir chevron energy technology company spe 95531, 95528, 89753, 89754, 100384. Condensate is mainly composed of propane, butane, pentane and heavier hydrocarbon fractions. 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. According to the complexity of the reservoir fluid phase behavior, reservoir modeling is classified under two distinct groups. Africa subsahara total reported a naturalgascondensate discovery on block 11b12b in the outeniqua basin, 175 km offshore southern south africa. Simulation of gas condensate reservoir performance keith h.
Understanding the behaviors of gas condensate reservoirs. The development of gascondensate reservoirs by gas injection is treated in chapter 12. Pdf understanding the behaviors of gas condensate reservoirs. Formation damage in gas condensate reservoirs can be caused by a buildup of fluids condensate around the wellbore. Its presence as a liquid phase depends on temperature and pressure conditions in the reservoir allowing condensation of liquid from vapor. It is shown that both the temperature and composition of the injection fluids play a key role in the remediation of productivity and condensate recovery. As the exploration for natural gas is extended to deeper horizons, more reservoirs.
Experiment and simulation study on the special phase. 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. The gas is much more mobile than the condensate and, therefore, the gascondensate ratios gcr exhibited at surface are commonly higher than that of the reservoir fluid. One question often asked is during and after sampling. A commercial simulator was then used to carry out numerical reservoir simulation of fluid flow in the north field. Gas condensate field produce mostly gas, with some liquid dropout, frequently occurring in the separator. Gas condensate is one of the most different fluids in reservoir simulation due to retrograde condensation in case of pressure reduction.
The gascondensate content in gases of various deposits ranges from 12 to 700 cm3 per 1 m3 of gas. The column, 23m long, 3mm thick is packed with small particles of solid ceramic material. Ron terry discusses gas condensate reservoirs, calculating hydrocarbon. From equation 1 we can derive the ratio krgkro in region 1 as a function of pressure, the flowing fluid composition and the fluid pvt properties. It might happen in a lean gas condensate reservoir.
It is difficult for condensate blockage to be detected by any method other than finescale simulation. A simulator is a program used to perform material balance calculations to determine pressure and saturation distribution of the reservoir as a function of time. Large reservoir condensate removal pumps, condensate. The depletion of gas condensate reservoirs to pressures below the dew point has been studied by reservoir engineers for many years.
When the pbhf is above dew point, the mw of the surface liquid is the highest. There is a difference between current condensate recovery factor defined for a certain point of time and final condensate recovery factor defined as of the moment of termination of commercial development of the field. The brulpadda well encountered 57 m of net gas condensate pay in lower cretaceous reservoirs. Figure 1 provides a fairly typical gor versus total flow rate response from a gas condensate reservoir. A natural gas liquid with a low vapor pressure compared with natural gasoline and liquefied petroleum gas. Once an accurate model was obtained, the following three solutions to. With this foundation in place, they turn to the principles of fluid flow, water influx, and advanced recovery including a basic introduction to hydrofracturing.
Phase behavior is relevant to every aspect of petroleum and natural gas engineering. Every gas condensate reservoir provides a new example with a different set of conditions requiring different emphasis on which pvt data are important. Some gas species within the raw natural gas will condense to a liquid state if the temperature is reduced to below the hydrocarbon dew point temperature at a set pressure. Spe 63087 guidelines for choosing compositional and black.
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. In case of isothermal reduction of the formation pressure, part of them condenses in the form of gas condensate. Higher salinity formation waters tend to contain less dissolved gas. Pdf modeling production decline in liquid rich shale lrs gas.
The literature shows many differences between gas condensate reservoirs and dry gas reservoirsi6. In this study, we use decline curve analysis, reservoir. Gas condensate reservoirs are gas systems that reside in reservoirs with the original temperatures lying between the critical temperature, t c, and the cricondentherm t max in figure 2. In reservoirs the dissolved gas is mainly methane from 10 scfstb at psi to 35 scfstb at 10 000 psi for gaswater systems, and slightly less for wateroil systems. Next, they explain the material balance approach in depth, and demonstrate its application to singlephase gas, gascondensate, undersaturated oil, and saturated oil reservoirs. The phase diagram shows the retrograde gas field must have a temperature higher than the critical point temperature.
Gascondensate reservoirs are thermodynamically complex and require. This page discusses condensate banking and how to overcome its effects. The formation of liquid hydrocarbons in a gas reservoir as the pressure in the reservoir decreases below dewpoint pressure during production. Lean gas condensateleanlean gas condensate gas condensate rich gas condensaterichrich gas condensate gas condensate 0 0. 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. Ngl vs lng vs lpg vs natural gas vs condensate natural gas liquids natural gas liquids ngls vs lpg vs lng talk about alphabet soup ngl vs lng vs l. Chapter 5, part 1 of the online course in applied petroleum reservoir engineering. It consists of shallow marine sands deposited over a broad shelf.
Us3149668a gas recovery from gas condensate reservoirs. Naturalgas condensate, also called natural gas liquids, is a lowdensity mixture of hydrocarbon liquids that are present as gaseous components in the raw natural gas produced from many natural gas fields. An experimental phase diagram of a gas condensate reservoir article in petroleum science and technology 3020. In this kind of fluids, two phenomena named negative inertia and positive coupling, become significant in the high velocity zone around the wellbore. Gas injection techniques for condensate recovery and. Spe, iniercomp resource development ana engineering, inc. Currently, most of this petroleum is in the fields that are onshore or on the continental shelf in.
Effective vaporizer for recovering retrograde hydrocarbon condensate from a gascondensate reservoir. Look here to find little giants vcl14, vcl24uls, and vcl45 series of large reservoir condensate removal pumps. Often times, it is safe to assume that reservoir fluid behavior is only a function of pressure and independent of. Condensate blockage might play an important role in reduction of the well deliverability of a gas condensate reservoir. The liquid is sometimes called by an older name distillate, and sometimes simply oil. The term wet gas is sometimes used as more or less equivalent to gas condensate. 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. What is the difference between a wet gas and a condensate. Modeling a rich gas condensate reservoir with composition.
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