This paper presents the results of an extensive study and field test carried out at the site of Prudhoe Bay's four oily waste injection wells. The field work was part of an overall environmental assessment intended to: (1) confirm earlier results indicating that no fluid communication was occurring with the permafrost; (2) determine optimum conditions for the disposal of waste in the presence of hydraulicallyinduced fractures; (3) substantiate that an increased injection pressure could be safely implemented.A three day inject·ion test, including a step-rate stage, was carried out. Data collected included surface and downhole pressures, in-situ stress measurements, and monitoring of ground surface deflections and wellbore hydraulic impedance.Radially symmetric surface tilt patterns showed that the test ·well connects to a horizontal fracture of 60-foot radius. Wellbore impedance indicated that a horizontal fracture with 9-18 foot radius communicated with the well. Integration of rock mechanics, historical information, and the collected data provided a clear picture of what was occurring underground. The different evaluation techniques showed consistent results as reflected in the estimated fracture size, placement and damage zone properties.
This investigation of multiphase flow, supported jointly by the Texas Petroleum Research Committee, The University of Texas, and many companies affiliated with the oil industry, is an effort to develop a reliable method of predicting static pressure loss during two-phase horizontal flow in 2-in. pipe. The 165 two-phase tests were run in 1688 ft of 2-in. steel line pipe with water, distillate, and crude oil in connection with natural gas. The liquid flow rate ranged from 50 to 2500 B/D, with gas rates up to 6 MMscf/D. The range of mean line pressures was from 70 to 850 psig. Pressures were measured at 12 line locations, the liquid holdup was measured at two locations, and flow patterns were photographed through plastic pipe sections. From the data, correlations have been developed for liquid holdup and for an energy loss factor. The correlations can be used in conjunction with a derived equation to predict two-phase horizontal pressure losses. The prediction method is carefully outlined and, although it lends itself to computer usage, it is relatively fast and just as accurate by hand. Applied to the original data, the method yielded pressure gradients with an average error of 2.3 percent.
SMALL angle X-ray scattering curves have been obtained for a series of Na Wyoming Bentonite clay samples containing 10~o clay by weight and NaPOa in concentrations ranging from 0 to 100 meq/1. From the scattering data, the relative probability of spacings between parallel clay platelets was computed. For the sample containing no NaPOs, the probability distribution showed a relatively broad maximum at an interparticle spacing of about 180 ~. As the concentration of NaP O3 increased, the maximum became sharper and occurred for smaller interpartiele distances. At NaPOa concentrations between 25 and 100 meqfl, the position d of the maximum was given approximately by the equation d=21-b 18.4c-1/~, where d is in angstroms, and v is the NaPO3 concentration in eqfl. The similarity of this relation to the dependence of d on the concentration of NaC1 (Norrish and Rausell-Colom, 1963; Norrish, 1954) suggests that the interparticle spacing depends primarily on the sodium ion concentration and not on the concentration of the anion. The value of d appears to be independent of whether the gel was prepared by the method of lgorrish and Rausell-Colom, in which a dried flake was allowed to come to equilibrium with an electrolyte solution, or whether, as in this investigation, the gel was obtained by centrifuging a dilute suspension. Since the Na ions act to reduce the double-layer repulsion between platelets, while the anions tend to be adsorbed on the platele} edges and thus reduce the edge-to-face linkages (H. van Olphen, 1962), the value of the most probable interpartiele distance appears to be determined primarily by the magnitude of the double-layer repulsion, even though other properties of the clay gels, such as the rheological behavior, are governed mainly by edge-to-face attractions.
The main North Slope Class I industrial waste disposal facility has injected 12 million barrels into a permeable formation just beneath the permafrost at 2000 feet. Initial concerns about fluid confinement were addressed by extensive field testing. This testing, coupled with the absence of underground sources of drinking water, allowed injection pressures to be authorized above the fracture gradient - an unusual operating condition. Re-permitting the facility in 1999 required an evaluation of permafrost thermal response to the injection of warm fluids and determination of potential impacts on waste confinement. This was accomplished using temperature logging after a one week shut-in period and by thermal modeling. At issue was whether the temperature log profiles could be explained by conductive heat transfer or whether they indicated upward fluid movement out of the injection zone. The evaluation was accomplished by coupling a radial thermal model with a one-dimensional vertical conduction model. This combination could better predict the temperature profile adjacent to the injection interval because vertical heat transfer is dominant just above the storage reservoir. Very good agreement was obtained between field measurements and the model results, indicating there was no fluid moving upward through the confining zone. With this "history match" as a basis, the model was used to predict future temperature changes and thaw bulb growth throughout the permafrost interval. Introduction Five wells were drilled through the permafrost in 1973 for a field test to determine the thaw extent and casing loading that results from production of hot oil-reservoir fluids. The wells were located at the Prudhoe Bay Pad-3 facility and oriented on a 5-spot pattern with 33 feet between the corner wells (Figure 1). During this test, hot glycol was circulated in the five unperforated wells to thaw the permafrost. After 18 months, the individual thaw bulbs merged to form a single thaw bulb. This test and results are documented in Reference 4. Following the test, the wells were shut in until waste injection began in 1976 in the Northwest well. Injection began in the Northeast well in 1978 and in the two southern wells in 1985. Injection has alternated among the four corner wells during the past 23 years. The center well was never completed and the Northeast well was plugged and abandoned in 1988 due to mechanical problems. In 1989 three wells were permitted for Class I industrial waste disposal. The injected volume has now reached 12 million barrels (MMB). The wells are completed as shown in Figure 2. They are perforated 145–258 feet below the base of the permafrost in a heterogeneous interval of thinly-bedded sand stringers, siltstones, and mudstones. A very permeable 30 foot-thick sandstone comprises the upper part of the injection interval. The confining zone and arresting interval are composed of inter-bedded low permeability silts, shaley mudstones, and sand stringers. The aggregate thickness is 132 feet. Wastes are trucked to Pad-3 from various sources. These include drilling rigs, production facilities, well treatments, heavy equipment operations and maintenance, laboratories, and the de-watering of numerous pits. These volumes include a wide spectrum of waste types (1) (2) with a range of temperatures, viscosities, densities, and solids content.
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