heavy gas condensate reservoirs (>0.75) present interesting challenges in their study, production and reservoir management. Simulation and history matching are often hindered by the lack of appropriate PVT properties. Furthermore, it is well established that they experience properties. Furthermore, it is well established that they experience hysteresis effects following a shutin. Remedial action is cumbersome but possible. This work presents a simulation of the behavior of both lean and possible. This work presents a simulation of the behavior of both lean and heavy (rich) gas condensate reservoirs, shows radial liquid profiles for various flowing bottomhole pressures (compared with a phase diagram), demonstrates degree of gas relative permeability reduction and explains the hysteresis effect. Lean gas injection is a remedial action, reducing the near-wellbore liquid saturation. The study shows that the degree of the adverse gas relative permeability reduction can be minimized or tempered by the appropriate choice of the flowing bottomhole pressure, ie., production can be optimized. Introduction The producing rate of gas condensate reservoirs is affected greatly by the flowing bottomhole pressure and not only because of the pressure gradient in the reservoir. The value of the bottomhole pressure controls the amount and distribution of liquid condensate accumulation near the well with an unavoidable relative permeability reduction. The higher the gas gravity, the more the liquid condensate will be and therefore the relative permeability-to gas reduction will be more pronounced. The classification permeability-to gas reduction will be more pronounced. The classification of lean and heavy (rich) gas condensate has been presented by Cronquist. A separation between the gas condensate region and the volatile oil region appears to be at 11% heptane-plus. Figure 1 contains the initial condition of two reservoir fluids from two different fields that are studied in this paper. One of these is well within the lean gas condensate region where the paper. One of these is well within the lean gas condensate region where the second is very near the volatile oil line. This fluid can be readily classified as a heavy (rich) gas condensate. Fussell in a frequently referenced paper has stated "productivity (from gas condensate producing wells) is severely curtailed when the flowing bottomhole pressure is less than the saturation pressure of the in-place fluid." While this contention is true, the implication that gas condensate reservoirs can be produced with a bottomhole pressure above the dew point pressure produced with a bottomhole pressure above the dew point pressure ("saturation pressure" in Fussell's nomenclature) is rarely, if ever, feasible. A survey of several gas condensate reservoirs has shown that invariably, the initial reservoir pressure is at, or very near, the dew point pressure. As a consequence, to have any appreciable driving force in the reservoir, production from gas condensate reservoirs should be the result of an production from gas condensate reservoirs should be the result of an optimization of (1) The producing rate and the reservoir pressure in Eq. 1 are, of course, time functions while the relative permeability to gas, krg, is a function of both space and time. Therefore, to maximize the cumulative production within any time period (transient, steady state or pseudosteady production within any time period (transient, steady state or pseudosteady state) it is necessary to attempt a number of simulations ahead of time. This must be augmented by laboratory-determined relative permeability curves. There exists an optimum flowing bottomhole pressure for a given average reservoir pressure and operational constraints, that would result in a relative permeability reduction distributed in the reservoir and especially around the well, such that the product (P -Pwf) : krg is maximized. The bottomhole pressure "path", ie., its evolution with time is very important. Once condensate is formed near the well, very little can revaporize into the gas phase even if the pressure is built up to the original reservoir pressure. Thus, if a condensate well is shut in and then re-opened the production rate of the new flow period will continue largely unaffected by the buildup. P. 471

INA Oil Company, Plc. Zagreb is a Croatian company engaged in the exploration and production of oil and gas, refining and distribution of petroleum products. An enormous quantity of hazardous waste is generated in oil and gas production and thus has to be disposed in a permanent and safe manner. In recent years, INA has been disposing waste by injection into exploration dry wells and production depleted wells. A specific waste disposal problem has arisen in the process of gas and condensates in Molve, Kalinovac, Stari Gradec and Gola fields. Namely, mercury-sulfide, sulfur slurry and heavy metals have been separated during the production of gas and condensate. Mercury-sulfide has been separated in the process of active coal utilization. The disposal of active coal saturated with mercury-sulfide is a very complex issue. So far, the methods of mercury-sulfide disposal have not been ecologically acceptable. However, on the basis of new experience and knowledge in that field, waste dispersed in a bentonite suspension may be disposed in a permanent and safe manner into appropriate geological formations. In the same way, when combusting various types of industrial and municipal waste, the problem of residual ash disposal emerges. Such residual ash contains heavy metals which may be permanently disposed by using the above mentioned method. This paper deals with the experience of waste disposal by deep well injection in the Republic of Croatia. Introduction The exploration of hydrocarbons in the Republic of Croatia started some hundred years ago, and significant oil and gas reserves have been discovered. More then 4,300 exploration and production wells were drilled in the onshore and offshore sedimentary deposits. In the nineties, there was initiated to dispose waste, generated in the process of exploration, drilling, production, refining and distribution of hydrocarbons by injection into dry exploration or depleted production wells. At the time, the liquid waste component was injected into an abandoned, specially selected well, while its solid part was neutralized by solidification and it was disposed at the location of wells, namely in the existing mud pits or specially built waste disposal sites. Nowadays, by improving the referred technology, liquid and solid parts of waste have been permanently disposed by injection into geological and technically appropriate wells. The technology mentioned above enables not only the disposal of waste generated in oil industry but also that generated in other industries such as food industry, chemical industry, leather and pharmaceutical industries. By the application of the referred technology, waste may be permanently and safely disposed into geologically appropriate wells, as well as heavy metals which contain almost all kinds of waste, thus meeting the principles of environmental protection. The overall waste disposal cost and the possibility of polluting potable water by heavy metals from solidificated solid part of waste are reduced. Currently, the technological waste created during drilling, workover, oil and gas production and refining processes is permanently disposed by applying a specific procedure developed in Croatia. For that purpose, an adequate law regulation to enable the application of the referred procedure is under preparation. This paper deals with the possibility of hazardous waste disposal generated in the process of oil and gas production and by incineration treatment (residual ash). Many dry and depleted wells are particularly appropriate for a permanent disposal of industrial waste generated in various industries since there is no need for additional investment in the creation of new wells. Selected geological formations at the depth of 1,500 to 5,000 meters are covered with impermeable bed rock and cap rock without vertical regional faults, which prevents waste from migrating into the aquifer of potable water. Waste disposal by injection into deep wells is a unique method which may be used for a permanent disposal of hazardous waste without having a single impact on the environment, since waste is disposed out of the biosphere.

There has been a long tradition of process waste disposal into existing deep wells in Croatia. Previously, liquids were separated from solids and injected into geologically appropriate formations. Solids were left in the existing mud pits or transferred into selected deposits. An essential disadvantage of such a procedure was the settlement of heavy metals and their penetration into sediments containing fresh water. The authors of this project have elaborated a new technology that presumes joint injection of liquids and solids into deep wells properly designed, so that the slurry may penetrate through geologically adequate formations. Wells have been classified into three groups upon which the following requirements are imposed: (1) reservoir pressure of a selected geological formation is lower than the hydrostatic one; (2) reservoir pressure is higher than the hydrostatic one, but lower than the fracturing pressure of that formation; and (3) possibility of obtaining an injection pressure that creates fractures and thus enables waste disposal. With regard to the fact that a relatively large number of dry exploration wells and depleted production wells exist in Croatia, the study illustrates that a number of wells can be classified into these three groups. Currently, the technological waste created during drilling, workover, oil and gas production and refining processes is permanently disposed by applying a specific procedure developed in Croatia. Besides, there has been a serious debate over the possibility of a permanent low and middle radioactivity waste disposal created in health services, pharmacy and food industry, following the referred procedure. For that purpose, an adequate law regulation to enable the application of the referred procedure is under preparation.

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