A potential mechanism for part of the production decline observed in the Prudhoe Bay field is siderite (iron carbonate) scale deposition. This laboratory investigation focused on evaluating the effect of the existing downhole scale inhibitor program on the proposed siderite formation damage mechanism. A tube block test was employed to generate iron carbonate and evaluate commercial products for its inhibition. This study indicates that the current inhibition program for barium sulfate and calcium carbonate is not protecting against damage by iron carbonate deposition. The other products tested were also ineffective. Furthermore, precipitation of the scale inhibitors by iron(lI) is suspected. There is no field evidence of damage from this precipitation with the current inhibition program.

The souring of reservoirs by microbial activity has become a major concern to the oil and gas industry. In the present study, core flood experiments were used to evaluate the efficacy of periodic formaldehyde injection for the control of in situ biogenic reservoir souring. In these floods two reservoir environments were simulated: the near-injection well, and the deep-formation. Formaldehyde treatments were demonsrated to control souring in both enviroments; if the formaldehyde can be transported through the reservoir, in situ biogenic souring should be mitigated.

A methodology for evaluating a complex reservoir for an EOR process is presented in this paper. In this m~_tho~ology, two f~ctors are emphasized. First, ut1llzat1on ~f _a stag~w1s~ workplan with numerous go 1 no-~~ dec1s1on pornts 1s shown to be important in ~vo1d1ng t~e ~xpenditure of significant time and money rn the appl1cat1on of an EOR process to an inappropriate reservoir. ~econd, t~e importance of a multi-disciplinary workteam 1s emphasized. The tasks required to carry out such a _reservoir evaluation involve diverse knowledge a~d sk1lls beyond the ability of any one discipline. Frnally, the workplan must be tailored to the specific needs, or characteristics, of the reservoir.In this paper, we evaluate the South Cuyama Field for the application of Micellar-Polymer Flooding. The South Cuyama reservoir is a mature field in California that has b?th complex geology and a complex operational h1story. Two factors were found to be critical in determining the viability of the micellar process in South Cuyama. First, the faulted nature of the South Cuyama sands e~p_hasized the importance of sand continuity between InJectors and producers. Second, in order to make the EOR process profitable, the remaining oil in South Cuyama had to be large enough to justify the added expense of process implementation. This paper presents the results of a multi-disciplinary study by eng1neers, geologists and geophysicists from the Research, Engineering, and Operations organiz?tions. T~is study starts with preliminary reserv~1r screenrng based on average reservoir properties, progresses through the reanalysis of existing data to acquire an updated picture of the reservoir and determine the key questions to be answered describes a joint geological I geophysical study which 'included a 30, high-resolution seismic study, reports the results of 237 field work done in existing wells, presents the results of updated material balance and volumetric studies, and describes the drilling and coring of a reservoir delineation well along with the analysis of the core. Particular emphasis is placed on determining the amount and distribution of remaining oil saturation, which is studied by log-inject-log tests, single-well tracer tests, laboratory core analysis, reservoir performance, and OOIP studies. The progression of the workplan is in the order of increasing effort and expense. As key questions are identified and critical data found lacking, we progressed logically to the next step. The results of this study show that South Cuyama is not a good candidate for micellar-polymer flooding. Using the methodology presented here, we were able to determine this fact without actually running a pilot test, thereby saving considerable expense.

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