TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMature fields represent a special challenge in terms of drilling, because the net present value of the wells compared to the well investment diminishes with the degree of maturity. As the value diminishes, less and less time can be invested in reservoir studies to support field activities. Special workflows are therefore required to allow for a screening of potential infill drilling locations as well as a value assessment.The numerical simulation approach consisted of accounting for the difference between the simulation model and the actual production observations. Being able to account for the difference between model and reality allowed determining how much effort is required to come up with a "reasonable" model, when do we stop to do the history matching, and how to adjust the production forecasts to account for the difference between model and reality.
A technical feasibility study of a polymer-augmented waterflood process in San Francisco Field indicated that this enhanced oil recovery process might be commercially feasible. Since the feasibility study used hypothetical polymer properties, laboratory measurements of specific commercially available polymers were required. The experimental program was divided into three phases.A screening program to reduce the number of candidates. Basic fluid rheological data and quality were developed. For each polymer candidate, four polymer concentrations in three different salinity brines were prepared. Screen Factor tests, Filtration Ratio and viscosity measurements were obtained for each solution. The results were compared to select the best polymers for further testing.Core flooding experiments of the selected candidates. Parameters describing the rock polymer interactions (polymer adsorption and residual resistance factor) were developed. The polymer flow properties (viscosity versus shear rate) developed in the first phase were tuned to match the core flow experiments in a reservoir simulation model.A thermal aging study to verify that the selected polymer does not degrade significantly at reservoir temperature over time. This was a long-term test (six months duration). This paper describes the application of the procedures described in the American Petroleum institute publication RP63, dated June 1, 1990, "Recommended Practices for Evaluation of Polymers Used in Enhanced Oil Recovery Operations", and a case history of laboratory testing of polymer flood candidates. Introduction San Francisco Field produces from the Caballos Formation and is located in the Middle Magdalena Valley basin in Colombia, South America. San Francisco was discovered in 1984 and has been in production since that year. It is a heterogeous faulted anticline at 3000 ft depth. The initial pressure was 1100 psi and reservoir temperature is 45 C. Initial bubble point pressure was 950 psi. The API gravity of the oil varies from 23 to 28 degrees. 1 Caballos Formation is subdivided in Upper Caballos and Lower Caballos. Upper Caballos has a porosity that ranges between 12 to 23% and a permeability range between 20 md and 2000 md. Lower Caballos has a porosity variation between 9 to 19% and a permeability range from 10 md to 1500 md. 2 San Francisco Field is currently ungoing secondary recovery by water flood. A technical study showed that a polymer augmented waterflood process might be commercially feasible. The study used hypothetical polymer properties. To tune the study and to define the proper polymer for the process, a laboratory testing program was designed. Samples of water soluble polymers designed for use as mobility control agents in Enhanced Oil Recovery (EOR) operations and currently available in commercial quantities were solicited from several vendors. Experimental Materials and Methodology The samples of polymer tested, with some of the main properties, are listed in Table 1.
Breathing new life into a mature oil field is a challenge that has been facing national and private oil companies for almost as long as the oil industry has been in existence. Oil production from mature fields accounts for approximately 70% of the worldwide oil production. Unfortunately, more often than not, mature oil fields equate to high cost and low productivity, making mature fields unattractive when competing for resources with other options in a company's portfolio of investments. Major opportunities for production optimization in mature oil provinces are typically scarce, more so, if throughout the long lives of the fields nearly all conventional optimization strategies have already been attempted and implemented. The re-development project presented in this and its companion paper1 (SPE 104041) looked at the technical and business opportunities for two main re-development components. The first component aims to beat the natural production decline curve via the implementation of a massive infill drilling program; the second component aims to maintain production levels through the integration of various Improved Oil Recovery (IOR) methodologies. A multi-disciplinary team studied and recommended the implementation of a massive infill drilling program in a portion of Block 10, operated by Petrobras Energia Peru S.A. in the Talara area of Peru, to improve recoveries in a column of over 2,500 ft of shaly sands, with absolute permeabilities not higher than 1 md and with average well spacing already in the order of 20 Acre. The study included the design of the facilities to process and handle the incremental production. Analyses confirm that a massive infill drilling program would significantly increase the production in a period of 4 years, from current 3,200 bopd. The study also identified the areas with best potential for infill drilling. Among the sub-products developed in the study were a new production database to facilitate the task of mapping and calculating volumetrics, and a new methodology to estimate average net pay thickness from limited log information. The approach and methodologies developed for this project can be used to give new life to mature oil provinces around the world. Introduction The Block 10 (Lote X) of Petrobras Energia Peru S.A. (PESA) is located in the Talara basin, in the northwestern coastal region of Peru (Fig.1), and has an area of 470 sq. Km, all onshore. Oil and gas has been exploited in Block 10 since the early 1910's, mainly from formations of Tertiary age lying at depths ranging from 500 ft to 7,000 ft. As of today, there are in excess of 5,600 wells drilled in Block 10 and the current production is about 12,500 bopd. Perez Companc S.A., a company that was later acquired by PESA, started operations in the block in December 1996. For field management purposes, PESA has sub-divided Block 10 into four areas, namely Coastal, Central, Eastern and Southern (Fig. 2), comprising a total of 17 fields. For reservoir management purposes, the producing formations in Block 10 are grouped into Shallow, Intermediate and Deep formations. The investigation to asses the potential for a massive infill drilling program focuses exclusively on the Coastal area of Block 10, and on the Intermediate (Lutitas Talara, Echino and Ostrea) formations. Figure 3 is a generalized stratigraphic column of Block 10. The history of the Talara basin is very complex from the structural standpoint. It has been associated to subduction phenomena generally connected to tectonical and sedimentary processes, with mainly extensional events that generated intense distensile faulting. In the case of the Talara basin, the normal faults act as permeability barriers and also limit the continuity of the reservoirs. Figure 4 shows a structural map of the Coastal area of Block 10 at the Echino level, while Figure 5 is a cross-section selected arbitrarily, both with the purpose of illustrating the structural complexity of the reservoirs in Block 10. Note that for the purpose of this study, the Coastal area has been further sub-divided into five sub-blocks (Fig. 4).
Breathing new life into a mature oil field is a challenge that has been facing national and private oil companies for almost as long as the oil industry has been in existence. Oil production from mature fields accounts for approximately 70% of the worldwide oil production. Unfortunately, more often than not, mature oil fields equate to high cost and low productivity, making mature fields unattractive when competing for resources with other options in a company's portfolio of investments. The re-development project presented in this and its companion paper1 (SPE 104034) looked at the technical and business opportunities for two main re-development components. The first component aims to beat the natural production decline curve via the implementation of a massive infill drilling program; the second component aims to maintain production through the integration of Improved Oil Recovery (IOR) methodologies. A multi-disciplinary team studied and recommended the implementation of a program to drill a massive number of infill wells in a portion of Block 10, operated by Petrobras Energia Peru S.A. in the Talara area of Peru, to improve recoveries in a column of over 2,500 ft of shaly sands, with absolute permeabilities not higher than 1 md and with average well spacing already in the order of 20 Acre. A second objective for the study team consisted of evaluating the technical feasibility for a massive waterflood project, including a preliminary design of the surface facilities necessary to collect, process and inject seawater. The third objective consisted of investigating the technical feasibility for miscible gas flooding into an equally tight reservoir, together with the facilities to collect and inject the gas. Both injection projects required consideration of the processing needs for the incremental oil, water and gas production. Traditional optimization technologies were also revisited, including the hydraulic fracturing of the infill wells to attain initial productivity gains of 25% with respect to that of current wells, but without impacting the completion cost. Based on analytical and numerical analyses, it was found that a massive waterflood would extend the production plateau reached by infill drilling and produce additional reserves. The study also found that to be able to displace oil in the Mogollon formation it would be necessary to inject gas at pressures in excess of 3,000 psi. The approach and methodologies developed for this project can be used to give new life to mature oil provinces around the world. Introduction The Block 10 (Lote X) of Petrobras Energia Peru S.A. (PESA) is located in the Talara basin, in the northwestern coastal region of Peru (Fig.1), and has an area of 470 sq. Km, all onshore. Oil and gas has been exploited in Block 10 since the early 1910's, mainly from formations of Tertiary age lying at depths ranging from 500 ft to 7,000 ft. As of today, there are in excess of 5,600 wells drilled in Block 10 and the current production is about 12,500 bopd. Perez Companc S.A., a company that was later acquired by PESA, started operations in the block in December 1996. Paper SPE 104034 provides additional background information on the structural complexity of the block, general stratigraphy and the reservoir management structure put in place by PESA. For the sake of completeness, a generalized stratigraphic column of Block 10 is included as Figure 2, while Figure 3 shows an arbitrarily selected cross section of Block 10 included here to illustrate the severe degree of faulting, which is a problem particularly important when investigating the feasibility of re-development opportunities such as waterflooding or miscible gas flooding.
Bahrain Island is surface expression of a large anticline at depth - the Awali Field. It is one of the oldest producing fields, since 1932, in Middle East. Known producing reservoirs are in Cretaceous and Jurassic. In 1980s, E & P companies in Middle East started looking further below known reservoirs and there was regional success in Paleozoic Unayzah and Khuff Formations, which opened up new exploration frontiers in deeper gas. By late 1980s recognition of Paleozoic petroleum system started in Middle East. Discoveries made in Devonian reservoirs in Bahrain, Saudi Arabia & Turkey; Ordovician reservoirs in Jordan, Carboniferous reservoirs in Syria, and Silurian & Ordovician reservoirs in Iraq. Authors attempted examining and assessing 325 Sq Km of 3D seismic and 400 line km of 2D seismic data, with six deep wells. Considerable Paleozoic section is deposited at Awali field and the anticlinal structure continues well into it, thus forming a basis for exploring an entrapment potential as deep gas play. Horizons interpreted below, producing Khuff and Unayzah, have numerous potential structures and their associated reservoirs in Jubah, Jauf, Tawil, Ra'an, Hanadir and Saq formations. The potential source rocks, such as Qusaiba Shales, also lie within Paleozoic section. Jauf reservoir of Devonian age is found to be gas bearing, and it needs appraisal and development. Fault Trap play anticipated for Jauf and below reservoirs. Its analogue has proven successful on the flanks of Ghawar structure in Saudi Arabia. Seismic data interpretation suggests some stratigraphic truncations, in lower parts of Paleozoic section and on the flanks of its structure, which in turn create a stratigraphic play. Considering high potential of hydrocarbon accumulation in Paleozoic, further exploration efforts are needed and authors initially propose new seismic acquisition campaign specially designed for imaging deeper plays in Awali.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractBreathing new life into a mature
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