Rows Of Wells Research Articles

Application of Well Test in Daqing Oil Field

Abstract Well testing methodology was modified for Daqing field to account for the case in which rows of wells are brought on production and injection. Other applications of well testing are given including analyzing the effectiveness of fracturing, and detecting distortion of casing in a water injection well. An example is given of using well tests to evaluate the effectiveness of a lime suspension treatment to plug a large channel. Examples are also provided of how interference tests were used in conjunction with tracer testing to evaluate inter-well communication and fracture direction.

New Pilot Plant Studies at the Budapest Waterworks

Abstract The quality of water provided by the Budapest Waterworks should comply with the standards prescribed by the European Community. According to these provisions, on one of the major water-producing regions (Csepel Island), rows of wells of 60,000 m3/day yield have been closed recently, and in the immediate future further plants would have been closed because of the high iron and manganese content of the water. The raw water obtained from 100 different wells will be purified by a water treatment plant of 150,000 m3/day capacity. Considering the high iron content (0.05–0.15 mg/L) and manganese content (0.05–0.2 mg/L), the raw water fails to comply with the requirements of the potable water standard. Since 1990, over a period of three years, we conducted water purification experiments in several stages. In these, three methods of oxidizing as well as single and double layer open rapid filters were applied to oxidize the manganese (and, to a lesser extent, the water) present in dissolved form, resp., to...

The Productivity And Optimum Pattern Shape For Horizontal Wells Arranged In Staggered Rectangular Arrays

Abstract In a previous paper(1), the authors analyzed the productivity of horizontal wells arranged in a regular rectangular pattern. It was shown that there was an optimum for the pattern shape (i.e. length to width ratio); methods were described for calculating this shape and the productivity of the well. In this paper, the analysis has been extended to similar patterns in which the rows of wells are staggered. The optimum shape and performance have been calculated in a similar manner to that in the previous paper. It is found that the staggered pattern has superior characteristics. It has a slightly higher productivity and, more importantly, it is much less sensitive to the shape of the pattern. Essentially, the same performance is found over a wide range of pattern shapes for any particular drainage area. Equations are given for predicting the well productivity in this preferred arrangement as a function of well length and pattern area for pseudo-steady state flow. Introduction This paper is a continuation of a previously presented analysis(1) regarding the regular pattern of horizontal wells extended to the pattern in which the rows of wells are staggered. Figure 1 shows the distribution of wells in the reservoir with part la showing a regular pattern, and 1b a staggered pattern. In both cases, each well of length L is placed in the centre of a rectangle having dimensions b × a. In terms of geometry, both patterns are equivalent if only the respective dimensions are equal. In the previous paper(1), the authors presented a method which made it possible to find the optimum pattern shape and predict the productivity of the well in a two-dimensional reservoir with a modification permitting the productivity evaluation in a three-dimensional reservoir. A similar method will be used to extend the consideration to the staggered pattern. Description of the Problem The pattern shown in Figure 1b contains a repeated "pattern cell" that has been shaded. It can be seen that all boundaries of the shaded rectangle are the symmetry axes, thus being no-flaw boundaries. This means the liquid cannot flow across the sides of the rectangle, but can flow along them. Inside the rectangle, there is another no-flow boundary which is shown arbitrarily by the thick, dashed line, and whose exact location is not yet known. It must separate the drainage areas of both wells draining the rectangle. The shaded area in Figure 1b is, obviously twice as large as that in Figure la. The problem is treated as two-dimensional, pseudo-steady state flow and thus described by the equation Equation 1 (available in full paper) with boundary conditions: zero pressure gradient normal to the sides of the shaded rectangle in Figure 1b. With constant compressibility of the fluid and constant values of permeability and viscosity, equation(1) can be reduced to Poisson's equation [ef Ref. 1], and further replaced by a system of difference equations. The procedure is described in detail in the literature(1–3). Ultimately, the shaded rectangle is treated as a grid pattern containing mm grid points.

Sampling design for groundwater solute transport: tests of methods and analysis of Cape Cod tracer test data : Water Resour Res V27, N5, May 1991, P925–949

Tests of a one-dimensional sampling design methodology on measurements of bromide concentration collected during the natural gradient tracer test conducted by the U.S. Geological Survey on Cape Cod, Massachusetts, demonstrate its efficacy for field studies of solute transport in groundwater and the utility of one-dimensional analysis. The methodology was applied to design of sparse two-dimensional networks of fully screened wells typical of those often used in engineering practice. In one-dimensional analysis, designs consist of the downstream distances to rows of wells oriented perpendicular to the groundwater flow direction and the timing of sampling to be carried out on each row. The power of a sampling design is measured by its effectiveness in simultaneously meeting objectives of model discrimination, parameter estimation, and cost minimization. One-dimensional models of solute transport, differing in processes affecting the solute and assumptions about the structure of the flow field, were considered for description of tracer cloud migration. When fitting each model using nonlinear regression, additive and multiplicative error forms were allowed for the residuals which consist of both random and model errors. The one-dimensional single-layer model of a nonreactive solute with multiplicative error was judged to be the best of those tested. Results show the efficacy of the methodology in designing sparse but powerful sampling networks. Designs that sample five rows of wells at five or fewer times in any given row performed as well for model discrimination as the full set of samples taken up to eight times in a given row from as many as 89 rows. Also, designs for parameter estimation judged to be good by the methodology were as effective in reducing the variance of parameter estimates as arbitrary designs with many more samples. Results further showed that estimates of velocity and longitudinal dispersivity in one-dimensional models based on data from only five rows of fully screened wells each sampled five or fewer times were practically equivalent to values determined from moments analysis of the complete three-dimensional set of 29,285 samples taken during 16 sampling times.

Sampling design for groundwater solute transport: Tests of methods and analysis of Cape Cod tracer test data

Tests of a one‐dimensional sampling design methodology on measurements of bromide concentration collected during the natural gradient tracer test conducted by the U.S. Geological Survey on Cape Cod, Massachusetts, demonstrate its efficacy for field studies of solute transport in groundwater and the utility of one‐dimensional analysis. The methodology was applied to design of sparse two‐dimensional networks of fully screened wells typical of those often used in engineering practice. In one‐dimensional analysis, designs consist of the downstream distances to rows of wells oriented perpendicular to the groundwater flow direction and the timing of sampling to be carried out on each row. The power of a sampling design is measured by its effectiveness in simultaneously meeting objectives of model discrimination, parameter estimation, and cost minimization. One‐dimensional models of solute transport, differing in processes affecting the solute and assumptions about the structure of the flow field, were considered for description of tracer cloud migration. When fitting each model using nonlinear regression, additive and multiplicative error forms were allowed for the residuals which consist of both random and model errors. The one‐dimensional single‐layer model of a nonreactive solute with multiplicative error was judged to be the best of those tested. Results show the efficacy of the methodology in designing sparse but powerful sampling networks. Designs that sample five rows of wells at five or fewer times in any given row performed as well for model discrimination as the full set of samples taken up to eight times in a given row from as many as 89 rows. Also, designs for parameter estimation judged to be good by the methodology were as effective in reducing the variance of parameter estimates as arbitrary designs with many more samples. Results further showed that estimates of velocity and longitudinal dispersivity in one‐dimensional models based on data from only five rows of fully screened wells each sampled five or fewer times were practically equivalent to values determined from moments analysis of the complete three‐dimensional set of 29,285 samples taken during 16 sampling times.

Type Incidence of Herpes Simplex Virus in Clinical Isolates from Patients with Herpes Genitalis

Isolates from a total of 228 patients with clinical herpes simplex were included in this study: 92 were from patients in their first episode and 136 were from patients with recurrent genital herpes...

Cold Lake Cyclic Steam Stimulation: A Multiwell Process

Summary Cyclic steam stimulation (CSS) typically is thought of as a single-well process. At Cold Lake, however, where steam injectivity is achieved by fracturing the formation, considerable interwell communication is observed. The result is usually the watering out of a producer by condensed steam from a neighboring injector. These interwell interactions greatly complicate steam-injection scheduling for commercial projects involving hundreds of wells but do not seem to reduce bitumen production in early cycles. Field experience indicates that steaming rows of wells sequentially with 50% overlap in injection time between adjacent rows significantly reduces water transfer between wells, increases the conformance of the injected heat, and reduces the field's tendency to form communicating well couplets. Exploratory numerical simulations show that the impact of steaming strategy on bitumen production is not significant until later cycles.

Changes in antibody avidity after virus infections: detection by an immunosorbent assay in which a mild protein-denaturing agent is employed.

In titrating serum immunoglobulin G antibody to viruses by enzyme-linked immunosorbent assay, we used two rows of wells for serial twofold dilutions of the serum; in one row, a low concentration of a protein denaturant, 0.5 or 1.0 M guanidine hydrochloride, was added to the diluent so that the binding of low-avidity antibodies to viral antigens on the solid phase was inhibited. We then compared the antibody titration curves obtained in the two rows. We found that the addition of the reagent resulted in a parallel leftward shift of the curves and that the extent of the shift was greater in early than in late sera from all of the three infections studied (Japanese encephalitis virus, rotavirus, and rubella virus infections). This procedure may be useful for estimation of the avidity of antibody in serum and, with further evaluation, may prove to be applicable to single-serum diagnosis of virus infections.

Evaluation and Design of a CO2 Miscible Flood Project-SACROC Unit, Kelly-Snyder Field

Investigations of alternative methods for improving recovery in the SACROC Unit showed that an inverted nine-spot miscible flood program consisting of injecting CO, driven by water would be the most effective and economical. Under such a scheme, the predicted ultimate recovery would be some 230 million barrels more than is expected from the original water injection program. program. Introduction The Kelly-Snyder field, discovered in 1948, is one of the major oil reservoirs in the U. S., having approximately 2 3/4 billion bbl of oil originally in place. The early performance history of the field indicated that the primary production mechanism was solely solution gas drive, which would probably result in an ultimate recovery of less than 20 percent of the original oil in place. The SACROC Unit was formed in 1953, and in Sept. 1954 a massive pressure maintenance program was started. Water was injected into a center-line row of wells along the longitudinal axis of the reservoir. This program, together with controlled production under unitized operations, has effectively rebuilt bottom-hole pressure, restored a large portion of the reservoir to liquid-saturated conditions, and stabilized producing GOR's at near solution levels. producing GOR's at near solution levels. Although the performance of the water injection program was very encouraging, technical program was very encouraging, technical representatives of the major Unit owners were constantly investigating potential methods of improving the ultimate oil recovery over that expected from the water injection program. In 1968, a technical committee, investigating potential alternatives, recommended that a water-driven potential alternatives, recommended that a water-driven slug of carbon dioxide be used to miscibly displace the oil in the non-water-invaded portion of the reservoir and that a pattern injection program be developed in this area to implement the slug process and improve ultimate oil recovery. This paper presents a summary of the methods used in evaluating alternatives and designing the final program of CO2 injection, which was begun in early 1972. Reservoir The Kelly-Snyder field, in Scurry County (West Texas) is the major unitized field among four contiguous fields along the 35- X 5-mile Canyon Reef formation. The formation is a Pennsylvanian age limestone occurring at an average depth of 6,700 ft and is a northeast-southwest trending massive reef buildup with thinner, gently sloping flanks. Formation thickness varies from an average of 800 ft on the crest of the structure to less than 50 ft on the flanks, and averages 213 ft over all. The SACROC Unit constitutes about 98 percent of the Kelly-Snyder field and includes 1,256 wells and just under 50,000 acres. The unitized reservoir is generally bounded on the east and west by porosity development and on the northeast and southwest by offsetting units. An oil/water contact, although poorly defined in some areas, occurs throughout most of the Unit area. Only very limited water influx was detected during pressure depletion, indicating a relatively small aquifer in the immediate area. A summary of basic reservoir data is given in Table 1. Reservoir oil was initially undersaturated at an original BHP of 3,122 psig, and had a solution gas content of slightly under 1,000 scf/STB and a bubblepoint pressure of 1,805 psig. P. 1309

A highly sensitive radioimmunoelectrophoreticquantitation of human α-fetoprotein

A highly sensitive radioimmunoelectrophoretic method of quantifying alpha feto-protein (AFP) which covers the sensitivity gap between immunodiffusion or similar techniques and radioimmunoassay methods is described. The procedure is as follows: The Iaurell monorocket technique is used. 10 cm by 10 cm gel plates are made in 2 steps. First a 2-cm broad cathode gel is made containing about 10 ng of radiolabeled AFP. Second the anodic part of the gel is made containing about .02% of antibody. At the border between the cathodic and anodic gel a row of wells is cut. Exactly 10 cm of samples or AFP standard was used. High-voltage electrophoresis (10V/cm) for 4 hours or low-voltage electrophoresis (3 V/cm) for 18 hours is carried out. After electrophoresis the gel is dried and autoradiography on a common X-ray film is used for localizing the rockets. Exposure time may vary from a few hours to a week. Using 125 iodine-labeled protein with a high specific activity as indicator 8-24 hours should be sufficient. With 131 iodine-labeled protein 4-8 hours are needed. Before developing the X-ray film the outlines of the glass plate must be drawn with a pencil. The lower limit of sensitivity is 20 ng/ml. Blurred appearance of the precipitates especially in low concentration may cause a diminished precision. However sera with a concentration of AFP below 500 ng/ml may be used directly without dilution.

Predicting Optimum Shut-In of Wells in Peripheral and Line Drive Waterfloods

Here is a method for computing the rate, reserve, and economic performance of floods as a function of water production at the time a well is shut in. By using a steady-state, stratified reservoir computer model to predict performance of producing wells shut in at different percentages of water, performance of producing wells shut in at different percentages of water, the most economical operating plan can be determined. Introduction Many fields have been waterflooded using a conventional five-spot pattern where no troublesome decision had to made as to when the producers should be shut in - one merely kept producing until the economic limit was reached. Recently, more and more peripheral and line drive patterns have been chosen peripheral and line drive patterns have been chosen as the proper operation. Many of these are cycling 75 to 90 percent of the injected fluid through some of the producers; yet, at the same time, other producers have scarcely responded. producers have scarcely responded. The operational decision that is faced is when to shut in the high water producers. Up to a point, the longer the producing wells are kept on production, the better the volumetric sweep of the water front will be. On the other hand, tardy shut-in of the wells will lengthen the flood's life, increase operating costs, and decrease the flood's dollar value. Optimization of the operation is what must be achieved. To optimize, a series of performance calculations must be made under varying assumptions of shut-in water cut (percentages of water produced) for the first row of wells, the second row, and so forth. Naturally, the last row of producing wells must not be shut in until the flood's economic limit is reached. The reservoir phenomena that must be dealt with in this type of analysis include:the effects of mobility ratio,the growth of areal sweep with water cut,the effects of reservoir stratification,well productivities, and in some casesthe effects of cross-flow. In the past, many papers have described models used to evaluate producing performance. These models range from a simple, inverted five-spot pattern program to two-dimensional numeric models pattern program to two-dimensional numeric models capable of predicting field-wide performance under the various assumed producing conditions. In this paper we will describe the use of a simplified model paper we will describe the use of a simplified model that is computationally fast enough to make it especially desirable in handling optimization studies. Model Description Fig. 1 illustrates how the model used in this paper visualizes a portion of a field. The area included in the model normally covers the area affected by one injection well. Within this area, the element is viewed as being composed of layers. Normally, five layers are sufficient. A throughput or rate technology incorporated in the model is based on that for a line drive pattern with one injection well located at one end of the pattern and producing wells placed at varying distances pattern and producing wells placed at varying distances toward the other end. The flexibility of the program is illustrated by the patterns represented in Fig. 2. The simplest system consists of one injection well and one producer (as illustrated, only a portion of the injection volume enters the pattern and a portion of the production flows from another pattern into the producer). producer). JPT P. 497

Pressure Observations and Water Densities in Aquifers and Their Relation to Problems in Gas Storage

Given here are criteria for flow in aquifers that contain water of varying density. In general, if we know the potential between two points we must also know the density of the water at all points along a given flow path between the two points in order to determine if water is flowing along the path. path. Introduction M.K. Hubbert's classical papers on groundwater flow were published in 1940 and 1953. Since then many people have applied his concepts to a variety of people have applied his concepts to a variety of problems including entrapment of oil, underground gas problems including entrapment of oil, underground gas storage, and groundwater flow. Although Hubbert's original ideas have been extended into many areas of investigation, one important area still needs some study and clarification. This is in the treatment of problems in the flow of underground waters whose density varies from point to point because of changes in the concentrations of point because of changes in the concentrations of dissolved solids. McNeal touches upon this question. In a personal communication he gave a procedure for correcting potentiometric surface maps in basins where water potentiometric surface maps in basins where water density varies; a pressure correction, Delta p(s), is subtracted from recorded pressures. (1) where p(sw) and p(fw) are specific gravities of salt and fresh water, respectively, and delta Z is the vertical distance over which each type of water exists. Hitchon says, "Flow in variable density water systems, such as exist in most sedimentary basins, may be empirically represented by using a standard density. He describes a method that involves dividing the area into discrete density regions. Using a best-value density, hydraulic head maps are made for each region and flow lines are constructed within each region. If there is no opposed flow between any two regions of differing densities, it may be concluded that the flow paths may be empirically represented by using a standard density throughout the system. Hanshaw and Hill say, "One can attempt to correct all the potentiometric data for salinity variations, but this is a difficult task. Not only must one correct for the density of water in the aquifer at the well site, but one must also consider the integrated density of all water in that aquifer which is at higher points on the potentiometric surface". potentiometric surface". None of these authors give the basis for their statements about density corrections. The derivation of their pressure corrections needs to be outlined. Terms such as "integrated density" need to be defined. And the implications of these density effects, especially with respect to possibilities for flow, need to be clarified. Hubbert discusses this problem briefly. In particular, he shows how to handle the case of a basin in particular, he shows how to handle the case of a basin in which the salinity of the water increases with depth. Pressure and density measurements are taken in a row Pressure and density measurements are taken in a row of wells extending downdip from the flank of the basin. A well in the middle of the row is used as a reference well; the density of the water in this well is used as a reference density. At each of the wells, the potential of the water having the reference density is calculated on the basis of this density and the locally measured pressure. The plot of potentials calculated in this pressure. The plot of potentials calculated in this manner vs distance shows whether the water is static (minimum in curve) or flowing (direction of flow is tangent to curve). P. 1492

Appraisal of Marsal's Extrapolation Method for Establishing Oil Recovery

Abstract A few years ago Marsal published a method of predicting oil recovery as a function of time for an edge-water-drive reservoir with several rows of wells. The method is based solely on oil- and water-production data obtained during a short period for the first row of wells and the gross productions (past and future) of all wells. This paper presents a streamlined version of the original publication and experimental evidence showing the reliability of this version. For this purpose scaled experiments were performed in a large model (750 X 500 X 23 cm, 24.4 ft X 16.2 ft X 8.9 in.) in which edge-water-drive reservoirs with three rows of production wells were simulated. From the results of the experiments it is concluded that the method gives a fairly accurate prediction of the future production behavior of the reservoir and enables us to select the most profitable production plan. Results obtained with the method were always slightly conservative. Introduction The calculation method developed by Marsal aims at forecasting future reservoir behavior. It can be applied to floods in which a number of down-dip wells are rapidly going to water. Essentially it is a method for predicting the future behavior of the up-structure wells on the basis of the observed behavior of the down-structure wells. As such, the method is especially useful for predicting behavior of edge-water drives toward several rows of wells. The requirement to be met for justifying the approach is identity of production mechanism in all regions of the reservoir. The attraction of the method then lies in the fact that it applies even when we have no complete description of the prevailing production mechanism. The original publication was in the German language and for this reason, perhaps. did not attract widespread attention. In our opinion it deserves to do so because it does offer in a simple way results which are in fair agreement with observed data. The aim of the present paper is to bring the method to the attention of a wider audience. The method in its most simplified form is reviewed and experimental data in support of it are presented. PRINCIPLES To show Marsal's principle. we will first write the continuity equation for very simple conditions, linear flow (in the positive x-direction) in an incompressible porous body [cross-section A(x), porosity (x)], saturated with incompressible fluids (oil saturation S).When the oil in this formation is displaced by water, injected at x = 0 (inlet face), we get S f(x)A(x) + q(t) = 0, ............(1)t x where q(t) is the total gross displacement rate and f the fractional oil flow. The equation can be solved if we make the assumptions: that the fractional oil flow (f) is a univalent function of saturation (S); and that the function is the same throughout the porous medium. Then: f = f(S) f df S= x dS x S df S(x) A(x) + q(t)= 0.t dS x Solving this equation with the method of characteristics, we obtainx t df(x)A(x) dx = q(t)dt,.............(2)dSo o for a constant saturation, dS= 0.dt To simplify the formulas, we write x(x)A(x)dx = Vp(t),......................(3) o and dfg(f) = f[f(S)] = g{f[S(x, t)]} =, .......(4)dS so that Vp(x)g (x, t) =, ..........................(5)We(t) JPT P. 12ˆ

An Approximate Method for Determining Areal Sweep Efficiency and Flow Capacity in Formations with Anisotropic Permeability

Abstract The effects of anisotropic or directional permeability on the areal sweep efficiency and the flow capacity are examined. The paper points out the importance of taking directional permeability into consideration in planning a flood. It analyzes the two-dimensional flow pattern associated with the skewed line drive for a unit mobility ratio. The direct and staggered line drives are treated as special cases of the skewed line drive. Analytical expressions are developed for the areal sweep efficiency at breakthrough and the flow capacity. They are related to the spacing between like wells, the distance between a row of injectors and the nearest row of producers, and the degree of skewness of the line drive. The latter quantity is defined such that it is equal to zero for the direct line drive and equals one-half for the staggered line drive. The a real sweep efficiency and the flow capacity depend also on the orientation of the flood pattern with respect to the principal axis of anisotropy. The paper provides a simple method for determining the a real sweep efficiency and the flow capacity for a formation in which the permeability in the bedding plane is anisotropic. Introduction Directional or anisotropic permeability is manifested by the ability of the formation to conduct fluids more readily along certain preferred directions. This situation occurs in many producing formations and is usually attributed to depositional features in which the sand grains are oriented in a preferred direction. In some cases it results from the formation of a major and a minor fracture system. Directional permeability should be taken into account in many phases of the production and exploration activities. Recognizing its existence in the formation of interest and planning accordingly can lead to increased recovery and substantial savings. For instance, the areal sweep efficiency in a water flood depends to a great extent on the orientation of the flood pattern with respect to the principal axis of permeability. Anisotropic permeability is specified by the directions of its three principal axes and the permeability along each axis. The principal axes of permeability are mutually perpendicular. This paper deals with the areal sweep efficiency at breakthrough and the flow capacity for formations with anisotropic permeability. The flood pattern considered consists of alternate rows of injecting and producing wells. The rows of wells are parallel and form a developed, skewed line drive which is illustrated in Fig. 1. The staggered and direct line drives are treated as special cases of the skewed line drive.

A Novel Pressure Maintenance Operation in a Large Stratigraphic Trap

Abstract This paper presents a discussion of a program of pressure maintenance for the Adena sand field, a shallow dipping stratigraphic trap having a large gas cap. It is concluded that a reservoir of this type be successfully water flooded by injection into a row of wells along the gas-oil contact. Reservoir and laboratory studies showed that water channeling in gas saturated streaks existing in the oil zone would not occur, and that an effective water barrier could be formed between the large gas cap and producing area. Studies indicated gas-oil contact water injection far superior to the other programs investigated. One year of field performance indicates that the pressure maintenance program is functioning satisfactorily. History of Development and Unitization In May, 1953, Falcon Seaboard Drilling Co. drilled the Snodgrass No. 1 in Sec. 20, T 1 N R 57 W, as a rank wildcat approximately 14 miles south of Fort Morgan. Colo. (Fig. 1). This well encountered gas in the J sand of the Dakota series and was completed for a good gas well in what is now recognized to be the gas cap of the Adena field, the largest oil field in the Denver-Julesburg Basin. This well created only mild interest in this area of the basin and the next few wells drilled were considered to have but slightly more than wildcat prospects. The oil discovery came in Nov., 1953, when an independent operator completed the Cochran No. 1 in Sec. 12, T 1 N, R 58 W, flowing 900 bbl of 42 gravity oil from the J sand. The Adena J sand field is approximately seven miles long and 3.5 miles wide. The oil zone has an areal extent of approximately 8,425 acres and the gas cap covers approximately 4,650 acres. Basic reservoir data is shown in Table 1. Production is primarily from the Dakota J sand of Cretaceous age, encountered at an average depth of 5,650 ft. The formation dips gently to the west at a rate of only 48 ft per mile, with minor nosing and flattening within the field proper (Fig. 2). Basically, the field is a stratigraphic trap, with local structure playing a very minor role as a trapping component. Oil accumulation is controlled by permeability barriers on the east, north and south sides of the field, and by a shale seal at the base of the first bench. The formation is a light gray, fine-to-medium grained grindstone. To date 170 oil wells and 15 gas wells have been drilled. The gas wells have been shut-in since completion to conserve reservoir energy. Wells were completed by drilling the entire sand section, running 5.5-in. casing and perforating the pay interval. It took only two weeks to drill and complete a well. Approximately 85 per cent of the wells in the field were both cored and logged.

The Encroachment of Injected Fluids Beyond the Normal Well Pattern

Published in Petroleum Transactions, AIME, Volume 204, 1955, pages 79–85. Abstract In predicting the sweepout pattern efficiency to be expected in a secondary recovery operation, the reservoir engineer is often confronted with a situation in which part of the producing formation lies between the last row of wells and the reservoir boundary. To date, there has been little or no reference in the literature to sweepout pattern efficiencies in such areas. This paper presents the results of a laboratory study in which the area contacted around the edge of a reservoir injected in a five-spot pattern was determined. The X-ray shadowgraph technique was used in this study. It was found that surprisingly large portions of the reservoir area lying outside the well network are contacted by the injected fluid before abandonment conditions are reached. In fact, it can be said that at least 90 per cent of the area lying outside the last row of wells and within a distance of one well spacing of these wells will ultimately be contacted by the injected fluid in the case of most water floods. From the results given in this paper, it is possible to estimate not only the extent to which encroachment into these areas will occur but also the injection volume necessary to produce the wells to abandonment conditions. Introduction While considerable work has been done in recent years evaluating the fraction of the reservoir contacted as a function of the mobility ratio for several different well patterns, there has been practically no mention of what happens to the oil in that portion of the reservoir which lies between the last row of wells and the reservoir boundary. In fact, the assumption is generally made that little or no recovery can be expected from this area.