In this reservoir study of the Clinton sand, East Canton oil field, Ohio, results indicate that a properly engineered waterflood may be feasible for secondary oil recovery. Waterflood forecasts that account for a wide range of reservoir conditions are included and can be used for preliminary waterflood performance estimates. Introduction The Morgantown Energy Research Center of the U.S. Bureau of Mines has, for several years, engaged in studies of eastern U.S. oil reservoirs. The goal has been more efficient recovery and more nearly complete recovery of oil through the application of the various secondary-recovery mechanisms. The East Canton oil field in northeastern Ohio was selected for this study because of the impact of its potentially large reserves on the supply of Pennsylvania potentially large reserves on the supply of Pennsylvania Grade crude oil. Because of the unusual reservoir characteristics, secondary-recovery operations in the Clinton sand will be especially challenging for operators and engineers. Previously published reports dealt with reservoir geology and primary recovery in the East Canton field. It was recently reported that waterflooding might be feasible under certain conditions. Here we shall describe, in more detail, the reservoir factors that pertain to waterflooding, and provide the operators with a method for estimating possible oil production by waterflooding from their properties in production by waterflooding from their properties in the East Canton field. Location, History, and Development The East Canton oil field is composed of an or parts of 11 townships in Stark, Carroll, and Tuscarawas Counties in northeastern Ohio (Fig. 1). Active drilling started in 1965 in western Rose Township, Carroll County. Rapid development of the East Canton oil field, however, did not start until Oct., 1966, when the discovery well of the East Canton pool was completed. To date, the western and northern limits of the field have been defined, but the eastern and southern edges of be extended by future drilling. At present, the proved to semiproved productive area is approximately 22 miles long and 5 to 7 miles wide. By July, 1970, over 1,000 wells had been drilled, and several operators were drilling additional wells. Although ultimate primary recovery will vary depending on reservoir characteristics, volumetric calculations indicate recoveries between 28,000 and 63,000 bbl/well, based on 40-acre spacing. More recent decline curve analysis for a 15-well study area shows an approximate primary recovery of 43,000 bbl/well, using an economic limit of 90 bbl/well/ month. Initial production rates of individual wells in the field, as reported by completion records, ranged from a few barrels to over 300 BOPD after fracturing. Most wells produce from a few thousand cubic feet to several hundred thousand cubic feet of gas per day. Initial bottom-hole pressures of approximately 1,500 psi have been observed. Very few wells were plugged psi have been observed. Very few wells were plugged as dry. Peak production of the fieldapproximately 13,000 B/D was reached in Aug., 1968. Cumulative production passed the 10-million-bbl mark by July, production passed the 10-million-bbl mark by July, 1970. JPT P. 1371
One of the major problems associated with EOR in general and with CO2 flooding in particular is the tendency of the displacing fluids to bypass most of the crude oil in the flood pattern. The high mobility CO2 seeks out the path of least resistance through the largest pore openings and taken the most direct route between the injection well and the production well. Mobility control is, therefore, an important problem in CO2 flooding. Several methods have been problem in CO2 flooding. Several methods have been used in an attempt to alleviate the situation, but none have been successful to a satisfactory degree. One way to overcome the tendency of CO2 to bypass the residual oil would be to plug the large pores by forming solid materials in the individual pore spaces through in situ chemical precipitation. Several relatively inexpensive salts of the alkali earth group that are soluble in water react with CO2 to form solid carbonates that can plug the pores. Once the precipitate is formed in the large pores, subsequent precipitate is formed in the large pores, subsequent fluid flow will be forced to take place through alternate pore paths, thus, increasing the ultimate recovery. The overall objective of this study has been to evaluate the technical feasibility of utilizing carbonate precipitation for mobility control in CO2 flooding. The preliminary experimental work indicated that the carbonate precipitation can occur under various reservoir pressures and temperatures when the pH ranges between 7 to 8. Berea sandstone core samples have been utilized to study the effects of carbonate precipitation relative to altering/reducing permeability under a variety of pressures and permeability under a variety of pressures and temperatures. The results indicate that the permeability ran be significantly reduced by in situ permeability ran be significantly reduced by in situ carbonate precipitation. In order to further investigate the nature and extent of precipitation propagation in the core samples, a number of propagation in the core samples, a number of experiments have been conducted in pairs of cores connected in parallel and series. The results indicate that the carbonate precipitation is not localized in the core samples and the permeability profile can be altered successfully. Further relative permeability experiments verify the effects of the carbonate precipitates on the flow behavior of the cores. precipitates on the flow behavior of the cores Introduction CO2 flooding of one of the most promising enhanced oil recovery methods. The recovery efficiency, as with any fluid-driven process, depends on the degree of bypass or channelling created by the mobility of the displacing fluid. CO2, because of its high mobility compared to reservoir crude oil, has a tendency to bypass a high percentage of the reservoir pore volume. This causes early breakthrough and reduces the process's recovery efficiency. As a result, CO2 flooding is not economically feasible without better CO2 mobility control. Several methods of mobility control have been attempted with only limited success; therefore, now concepts for controlling the mobility of injected CO2 are required to increase the overall recovery efficiency and economics. One method of overcoming the tendency of CO2 to bypass the smaller pores which contain the residual oil, would be to selectively plug the larger pores. Once the larger pores are plugged, the pores. Once the larger pores are plugged, the subsequent CO2 flow must take place through relatively smaller pores. This will increase the areal and vertical sweep efficiencies and ultimate oil recover. To selectively plug larger pores in a heterogeneous porous media, in situ chemical precipitation can be employed. Several relatively precipitation can be employed. Several relatively inexpensive water soluble salts of the earth alkali group react with CO2 to form precipitate. One method of CO2 injection, known as WAG, employs alternate slugs of water and CO2. If one of the above mentioned chemicals is dissolved in the water slug, precipitation will take place in each pore where the precipitation will take place in each pore where the CO2 slug contacts its. The majority of the precipitate will, however, form in the high permeability zones where CO2 can flow moist readily. P. 53
A significant quantity of oil is left in reservoirs after conventional oil recovery techniques have been applied. In West Virginia and Pennsylvania alone, this oil has been estimated at over 4.5 billion barrels (0.72 billion m3). Conventional recovery methods are already being used when applicable. But a new recovery method is needed for use in reservoirs that have been abandoned. One alternative method for recovery of the residual oil is known as "oil recovery from underground drill sites". This recovery technology is a combination of proven methods and equipment from the petroleum, mining, and civil construction industries. Underground oil recovery can be an economically viable method of producing oil. This has been shown in producing fields, field tests, and feasibility studies. Faced with decreasing domestic oil production, the petroleum industry should give serious consideration to the use of oil recovery from underground drill sites as a safe, practical, and environmentally sensitive alternative method of producing oil from many reservoirs.
A method of predicting waterflood performance has been developed that combines certain facets of several previously published prediction techniques. The manner of combination has required the development and use of some new and some little-known relationships and has eliminated several of the weaker assumptions inherent in the original individual prediction methods. This approach, which was designed for computer solution, has removed the necessity of referring to plotted curves and permits the analytical prediction of waterflood performance for a five-spot well pattern in either homogeneous or stratified reservoirs. The predicted values are expressed in common oilfield units rather than in abstract or dimensionless terms.
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