ماهنامه اکتشاف و تولید نفت و گاز
پیاپی 77 (اسفند 1389)

Most of the Iranian oil fields are fractured; these reservoirs tend to produce at high rate in their early production time followed by low rates later on, leading to low overall recovery. Secondary and tertiary recovery processes based on gas injection can extend the life reservoirs by maximizing the oil recovery especially in fractured reservoirs.However, the injection strategy needs to be studied carefully to optimize the overall efficiency. One of the best methods to find out the effectiveness of a certain process for reservoir development is building a small model representing all the properties of that reservoir with lesser complexity in order to gain the results much faster and easier. So in this paper immiscible gas injection is simulated using compositional model in a reservoir insouthwest of Iran and the effect of different parameters on gas injection performance and oil recovery is investigated and finally, the best scenario is selected.

The South Pars gas field in Persian Gulf is one of the largest offshore fields in the world. The shallow-marine Kangan/ Dalan carbonates (dolomite and limestone) sequences, dated from the Middle-Upper Permian to the Lower Triassic, are the main reservoir units. In this study, FMI log from six vertical and one deviated wells were used to analyze the fractures geometry and density. Meanwhile their relationship with main geological features was the matter of interest. Interpretation of FMI logs with GeoFrame software shows that the natural fractures were developed generally in one of N-S, N80°-N100°, N40°-N50°or N140°-N160° trends. The similarity of these trends in all wells indicates the role of regional tectonic deformation on fracture formation. Preexisting deep seated faults reactivation, pre-folding regional compression in Zagros foredeep and related flexural basin are interpreted as the main tectonics.Fractures density doesnt change the lateral direction. However, the difference in the amount of shale is considered as a key role to control of the fracture distribution in the vertical direction. So increasing the shale volume in K1 and K3 units in compare with K2 and K4 is correlated with decreasing the fracture density in these units.

The most important part of the production technology is depended on engineering and installation of well completion equipments. The completion string is the most important component in petroleum production system and should be designed and installed precisely and maintained properly. The selection of equipments and techniques should be based on investigation of factors which are specific to the reservoir, wellbore and production system under study. The process of production optimization involves first understanding the reservoir fluid and effective parameters on its deliverability, then optimization the design of each well component in the line of flow, wellbore, completion and reservoir segment. This can be done through optimization of completion system, identification of restriction or the production limiting factors and specification meansof production efficiency increasing. Among mentioned parameters, tubing size has a special significance and should be determined properly. If the well suffers scale production, the completion string importance is multiplied. In this study the four major completion techniques commonly used for non-organic depositions is introduced. The subject has been case studied for one of southern Iranian oil wells with inorganic material production problem. The simulations were run using the Prosper software, and followed by sensitivity analysis and conclusive comparisons.

There are three types of gas reservoirs: 1-Dry gas 2-Wet gas 3-Gas condensate. The temperature in gas condensate reservoir is between the critical temperature and cricondenterm. When the reservoir pressure goes below the dew point pressure, due to reverse condensation in reservoir, gas becomes liquid. These condensate are excessivelybeing used in industry, if stay in the reservoir not only the condensate runs to waste, but also it decrease relative gas permeability near the wellbore, so that it will be decrease the well production. The changes in the flow rate and gas injection are of the techniques under the study to prevent or decrease the condensate saturation produced in thereservoir. This article examines changes in the Production flow rate and gas injection in the condensate production and saturation in reservoir.

Gas storage in salt cavern is one of the underground gas storage methods. This could be used as a complementary solution in the area that salt domes or salt layers exist. Different complicated parameters and obligations influenced the site selection for this proposes. In this article we focus on the parameters, which govern decision making on implication of salt cavern for gas storage.Diaprism, Tectonic activities, seismicity, surface and subsurface conditions of salt, its physical and chemical characteristics, hydrological and hydro geological conditions, economical, social and environmental restrictions are the main parameters should be take in to account for site selection. In addition to the exploration parameters, modeling procedures have also been discussed, which show multidisciplinary decision making method could be suggested for site selection propose.

One of the key elements of successful exploitation of tight gas reservoirs is the ability to fracture wells according to plan and production requirements. Most plans call for placement of multiple transverse fractures at specific locations within the horizontal well. Given the low productivity of these wells, the ability to successfully create multiple fractures is of paramount importance.A popular method of creating multiple fractures is to use frac ports and sliding sleeves. Open hole packers isolate different segments of the horizontal well. A sliding sleeve is placed between each packer pair and is opened by injecting a ball inside the borehole. Seating of the ball exerts pressure at the end of the sliding sleeve assembly, causing it to slide and open the frac ports.Once the port is opened, fluid is diverted into the open hole space outside the completion assembly, causing the formation to fracture. Proper operation of open hole fracturing systems requires attention to several wellbore environmental considerations.