Iranian Journal of Chemical Engineering (IJChE)

Abstract Marun oil field is located in the southwest of Iran and consists of two oil reservoirs named Asmari and Bangestan. Asmari oil reservoir has been producing sweet oil and gas since 1964, but for the first time a high amount of hydrogen sulfide gas was observed in one well of this reservoir in 1980. Moreover, the Bangestan oil reservoir is located deeper than the Asmari oil reservoir and has been producing sour oil and gas since 1972. This paper represents the conducted study on the determination of hydrogen sulfide oil pollution sources in the Asmari oil reservoir. There are two hypotheses for sources of hydrogen sulfide oil pollution in the Asmari oil reservoir; first, hydrogen sulfide gas migration from Bangestan oil reservoir and second, sour gas injection migration. Data of well souring history, hydrogen sulfide gas concentration of wells, volume of gas injection and RFT analysis were used to investigate these hypotheses. The results showed a similar trend of gas injection volume and hydrogen sulfide gas concentration of wells, which decreased over time. Also, the results demonstrated that the migration of gas injection is a source and cause of spreading of hydrogen sulfide gas in the Asmari oil reservoir.

Abstract Stuck pipe is one of the most serious drilling problems, estimated to cost the petroleum industry hundreds of millions of dollars annually. One way to avoid stuck pipe risks is to predict the stuck pipe with the available drilling parameters which can be employed to modify drilling variables. In this work, Artificial Neural Network (ANN) was used for stuck pipe prediction according to the fact that this method is applicable when relationships of parameters are too complicated. Based on the drilling fluid condition from one of the Iranian oil fields, stuck pipe instances were divided into static and dynamic types. The results of this study show more than 90% accuracy for stuck pipe prediction in the investigated oilfield. The methodology presented in this paper enables the Iranian drilling industry to estimate the risk of stuck pipe occurrenc during the well planning procedure.

Abstract Silica fume is a by-product of silicon metal or ferrosilicon alloys in smelters using electric arc furnaces. It consists of 85% to 95% amorphous silicon dioxide (SiO 2). Each individual particle of silica fume is spherical with average diameter 0.15-0.3 μm (100 times finer than cement particle); therefore its specific surface area is high. Silica fume particles are water wet and absorb excess water in cement slurry when cement slurry is extended by water. Silica fume thickens the cement slurry, so rheological properties are controlled by dispersants. In this paper, optimal concentration of silica fume and other additives for preparing 90 pcf cement slurry for liner cementing in one Iranian oilfield is determined. The criteria of designing slurry formulation are slurry density, rheological properties, fluid loss, free water, thickening time of cement slurry, and compressive strength and permeability of set cement. Finally, based on experimental results, the preferable slurry compositions are selected. This formulation can be used for cementing of oil and gas wells where moderate and light weight cement density is needed.

Abstract Production optimization ensures that wells and facilities are operating at their peak performance at all times to maximize production. This paper describes a procedure, to develop Inflow Performance Curves, Tubing Performance Curves and Choke Performance Curves, for one of the Iranian southern oil wells, from the results of a multiphase flow simulator (PIPESIM). The goal of this project is to optimize the production from one of the southern Iranian oil fields. Increasing the choke size leads to maximizing production, and causes an optimum reduction in wellhead pressure and bottomhole flowing pressure. Controlling flow patterns in all sensitivity analysis play a major role in selecting the proper variables. Using 7in. OD tubing size rather than 95/8 in. casing size and selecting 9/16 in. choke size rather than 7/16 in., the wellhead pressure between 700 to 1180 psia will be the result and optimum range in selected well No. 305b. The results show a successful experience in optimization of well No.305b and the production can be increased from 2000 BOPD to 3150 BOPD.