Withdrawal of oil and GAS from reservoirs causes a decrease in pore pressure and an increase in effective stress which results to a reservoir compaction. Reservoir compaction will result in surface subsidence through the elastic response of the subsurface. Usually in order to determine the subsidence above a hydrocarbon FIELD, the reservoir compaction must be first calculated and then the effect of this compaction on the surface should be modeled. The use of the uniaxial compaction theory is more prevalent and an accepted method for determining the amount of reservoir compaction. But despite of the reservoir compaction calculation method, there are many methods with different advantages and shortcomings for modeling of surface subsidence. In this study, a simple analytical method and semi¬-analytical methods (AEsubs software) were used for modeling of the surface subsidence of the SOUTH PARS GAS FIELD at the end of the production period.

In this paper we provide an introduction to real options in valuing investment projects. Since one of the real options applications is valuing oil and GAS development projects with high uncertainty and considerable investment costs, in this research we have performed valuation of selected phases of "SOUTH PARS" GAS FIELD development project. "SOUTH PARS" GAS FIELD as the greatest independent GAS FIELD in the world is shared between Iran and Qatar and contains approximately half of the GAS reserves of Iran. Based on the results of the model, using real options approach to valuing this project as compared to traditional valuation methods such as discounted cash flow, increases the project value meanwhile there is the possibility to identify optimal time of development.

The amount of GAS lift from the common FIELD of SOUTH PARS highly depends on the pattern FIELD development the by each party. This paper models the optimum production of GAS from a reservoir block of the SOUTH PARS FIELD and analyzes the effects of the economic parameters on the optimum path. Dynamic programming has been used to solve the optimization problem. To solve the problem numerically, state variables have been considered as discrete variables. According to the results, economic parameters including projected path of natural GAS prices and the government discount factor play important role in determining the optimum path of GAS production from the FIELD. Therefore, for the GAS FIELD under investigation, despite being a common FIELD between Iran and Qatar, the maximum potential production by the FIELD is not necessarily the optimum production for the FIELD. In this way, maximizing the return of the reservoir is not necessarily equivalent to maximizing the recovery factor of the FIELD. Accordingly, maximizing the economic return should be considered in the development of hydrocarbon FIELDs.

In many explored GAS reservoirs in the word, which are considered as GAS-GAS condensate reservoirs, many surface facilities receive the GAS as well as hydrocarbon condensates and water. Condensates cause slugs in a pipeline. The slugs, which are an aggregate of fluids, cause many problems in multiphase pipelines. Therefore, in order to separate condensates, slug catchers are normally used. A slug catcher is necessary equipment at the entry of a multi-phase flow processing factory. The specific performance of a slug catcher is the separation of GAS and liquid phases and temporary storage of the liquids. In this paper, we recommend a method for designing finger type slug catchers, based on two phase flow in principles. Then, using the proposed method, we design a slug catcher for the two present phases in the SOUTH PARS GAS FIELD. At the end, by considering condensate recovery and economical investigation of the suggested slug catchers, we choose the optimum slug catcher for these two phases. Among the most important results of this investigation, we can mention an efficient pattern for designing finger type slug catchers and the selection of the optimum one. Using this pattern is recommended for a proper design and reduction of time and costs.

The SOUTH PARS GAS FIELD is one of the SOUTHwestern FIELDs of Iran in Zagros sedimentary basin and consists of two Kangan and Dalan reservoirs. The Kangan and Dalan Formations belong to Dehram Group and are the most important GAS reservoirs in Persian Gulf area. Petrophysical characteristics in the studied well were evaluated by the data of the well logs and cores. For an accurate evaluation, the necessary corrections were applied on logs by considering the places of wash out, environment effects, GAS and shale effects. After that, the lithology of the Kangan and Dalan Formations were determined by using of cross plots of neutron-density, neutron-sonic, M-N plot, MID plot. On the based of Lithology, shale volume, presence of evaporite sediments and porosity, the Kangan Formation has been zoned to K1 and K2, and also the Dalan Formation has been zoned K3 and K4. The results show that the zone K2 of the Kangan Formation and the zone K4 of the Dalan Formation have an apporiate reservoir in terms of GAS saturation level, porosity and Lithology. Kangan Formation, Dalan Formation, SOUTH PARS FIELD, Petrophysical evaluation, Water saturation and GAS

The SOUTH PARS GAS reservoir, as the largest natural GAS supply source in the country, is one of the most important mega projects in Iran that has been used to develop its phases by various contractual methods. In this research a comparison between methods and the most appropriate contractual method has been identified which could be the basis for future development of GAS FIELDs or mega projects in the country. With the inclusion of criteria such as project risk for government, cost, quality, the integrity of implementation and production operations, project execution time, acquisition management know-how, by using “ Analytical Hierarchy Process” (AHP) method for contractual options, shows the superiority of the buy-back contract. The main features of the research that led to this conclusion are, the maintenance of the country's right to ownership, control of operations and costs by the state, transfer of technical know-how, acceptance of the risk of production and Perform 100% investment by the contractor and repayment it within 5 to 7 years after the commissioning of the FIELD products.