Pressure drawdown analysis for the Travale 22 well

This work presents preliminary results on the analysis of drawdown data for Travale 22. Both wellhead pressure and flow rate data were recorded in this well for over a period of almost two years. In the past, Barelli et al. (1975) and Atkinson et al. (1977) presented the analysis of five pressure buildup tests. Figure 1 shows the Horner plot for these cases. They found that to have a good match in all cases, it was necessary to assume that the Travale 22 well is intersected by a partially penetrating vertical fracture in a parallel-piped whose bottom side is maintained at constant pressure (boiling front), as shown in Fig. 2. Atkinson et al. also presented an analysis for a pressure interface test run in the Travale-Radicondoli area. In this case, the Travale 22 well was flowing and the pressure recorded at wells R1, R3, R5, R6, R9, and Chl (see Fig. 3 ) . Analysis of these data showed that pressure interference in this reservoir can be matched by considering pure linear flow (Figs. 4 and 5 ) . This indicated the possible presence of a vertical fracture intersecting the Travale 22 well. It was determined that fracture is oriented along the N73{sup o}W direction. In addition, the pressure interference data showed that no boundary exists within 2 kilometers from the fracture plane. It was mentioned that linear flow should take place in both horizontal and vertical directions

Research on oil recovery mechanisms in heavy oil reservoirs. [Quarterly] report, April--June 30, 1995

The goal of the Stanford University Petroleum Research Institute is to conduct research directed toward increasing the recovery of heavy oils. Presently, SUPRI is working in five main directions: (1) Flow properties studies -- To assess the influence of different reservoir conditions (temperature and pressure) on the absolute and relative permeability to oil and water and on capillary pressure. (2) In-situ combustion -- To evaluate the effect of different reservoir parameters on the in-situ combustion process. Ibis project includes the study of the kinetics of the reactions. (3) Steam with additives - To develop and understand the mechanisms of the process using commercially available surfactants for reduction of gravity override and channeling of steam. (4) Formation evaluation -- To develop and improve techniques of formation evaluation such as tracer tests and pressure transient tests. (5) Field support services -- To provide technical support for design and monitoring of DOE sponsored or industry initiated field projects. Accomplishments for this quarter are briefly described for each study

Research on oil recovery mechanisms in heavy oil reservoirs. Progress report, July 1, 1995--September 30, 1995

The goal of this research is to conduct studies towards the enhanced recovery of heavy petroleum. Five areas are being studied: flow properties; in-situ combustion; steam with additives; formation evaluation; and field support services. Progress is described

Transient foam flow in porous media with CAT Scanner

Transient behavior is likely to dominate over most of the duration of a foam injection field project. Due to the lack of date, little is presently known about transient foam flow behavior. Foam flow does not follow established models such as the Buckley-Leverett theory, and no general predictive model has been derived. Therefore, both experimental data and a foam flow theory are needed. In this work, foam was injected at a constant mass rate into one-dimensional sandpacks of 1-in diameter and 24-in or 48-in length that had initially been saturate with distilled water. The system was placed in a cat Scanner. Data, obtained at room temperature and low pressure at various times, include both the pressure and saturation distributions. Pressure profiles showed that the pressure gradient is much greater behind the foam front than ahead of it. Moreover, the pressure gradients keep changing as the foam advances in the sandpack. This behavior differs from Buckley-Leverett theory. The CT scan results demonstrated gas channeling near the front, but eventually the foam block all these channels and sweeps the entire cross section after many pore volumes of injection. Three series of experiments were run: (1) surfactant adsorption measurements; (2) gas displacements of surfactant-laden solutions and (3) foam displacements. The first two series of experiments were made to provide the necessary parameters required to match the foam displacements. To this end, it was necessary to smooth the saturation history data, using a Langmuir-type formula. A theory was proposed based on the principles of the fractional flow curve construction method. This foam theory treats the foam as composed of infinitesimal slugs of gas of varying viscosities. The foam front has the lowest viscosity and foam at the injection end has the highest

Transient pressure analysis in composite reservoirs

The problem of fluid flow in a radially composite reservoir is discussed. Recently published was the most general analytic solution available thus far. That analytic solution is analyzed, and the results are presented. The solution is dependent upon the following dimensionless parameters (if well-bore storage and skin effect are neglected): (1) dimensionless time based on the discontinuity radius, (2) the dimensionless discontinuity radius, (3) the mobility ratio, and (4) the diffusivity ratio. The range of parameters used in generating the results include dimensionless radius time of 0.01

Pulse testing in the presence of wellbore storage and skin effects

A pulse test is conducted by creating a series of short-time pressure transients in an active (pulsing) well and recording the observed pressure response at an observation (responding) well. Using the pressure response and flow rate data, the transmissivity and storativity of the tested formation can be determined. Like any other pressure transient data, the pulse-test response is significantly influenced by wellbore storage and skin effects. The purpose of this research is to examine the influence of wellbore storage and skin effects on interference testing in general and on pulse-testing in particular, and to present the type curves and procedures for designing and analyzing pulse-test data when wellbore storage and skin effects are active at either the responding well or the pulsing well. A mathematical model for interference testing was developed by solving the diffusivity equation for radial flow of a single-phase, slightly compressible fluid in an infinitely large, homogeneous reservoir. When wellbore storage and skin effects are present in a pulse test, the observed response amplitude is attenuated and the time lag is inflated. Consequently, neglecting wellbore storage and skin effects in a pulse test causes the calculated storativity to be over-estimated and the transmissivity to be under-estimated. The error can be as high as 30%. New correlations and procedures are developed for correcting the pulse response amplitude and time lag for wellbore storage effects. Using these correlations, it is possible to correct the wellbore storage-dominated response amplitude and time lag to within 3% of their expected values without wellbore storage, and in turn to calculate the corresponding transmissivity and storativity. Worked examples are presented to illustrate how to use the new correction techniques. 45 references

Further results determining permeability and thickness for a multi-layer five spot tracer test

This report presents further results obtained using a computer algorithm developed by Dexter Yuen, which gives an indication of the heterogeneity among the layers of a reservoir. Yuen, Brigham and Cinco-Ley presented a match obtained by this program with field data reported by Brigham and Smith. To find a more accurate fit for these data, the program was modified to allow the selection of up to ten peaks. Results of this more detailed analysis are presented

SUPRI heavy oil research program. Annual report, February 8, 1995--February 7, 1996

The goal of the Stanford University Petroleum Research Institute (SUPRI) is to conduct research directed toward increasing the recovery of heavy oils. Presently SUPRI is working in five main directions: (1) flow properties studies to assess the influence of different reservoir conditions (temperature and pressure) on the absolute and relative permeability to oil and water and on capillary pressure; (2) in-situ combustion to evaluate the effect of different reservoir parameters on the in-situ combustion process; (3) steam with additives to develop and understand the mechanisms of the process using commercially available surfactants for reduction of gravity override and channeling of steam; (4) formation evaluation to develop and improve techniques of formation evaluation such as tracer tests and pressure transient tests; and (5) field support services to provide technical support for design and monitoring of DOE sponsored or industry initiated field projects. This report consists of abstracts of reports and copies of technical papers presented or published

A RESERVOIR ENGINEERING ANALYSIS OF A VAPOR-DOMINATED GEOTHERMAL FIELD

The purpose of the study is to develop a simplified model to match past performances of a vapor-dominated geothermal reservoir and to predict future production rates and ultimate reserves. The data are fictitious, but are based on real data. A lumped parameter model was developed for the reservoir that is similar to the model developed by Brigham and Neri (1979, 1980) for the Gabbro zone, and a deliverability model was developed to predict the life and future producing rate declines of the reservoir. This report presents the development and results of this geothermal reservoir analysis

Effects of temperature on the absolute permeability of consolidated sandstone

The effect of temperature on absolute permeability has been a point of disagreement in the petroleum literature for many years. Recent work at Stanford University has shown no dependence on temperature of the absolute permeability to water of unconsolidated sand cores. The objective of this report is to extend the investigation to consolidated sandstone by following similar experimental procedures and observing whether any temperature effects exist. Fontainebleau sandstone was chosen as the core sample because of its low porosity and relatively clay-free composition. These characteristics allow the nature of consolidated sandstone permeability to be studied, while minimizing the effects of extraneous factors. Such factors, often present in Berea and Boise sandstones, include interstitital clay swelling in the presence of distilled water. Properties of sandstone differ from those of unconsolidated sand. Consequently, the effects of throughput water volume and flow rate, in addition to temperature, are studied. Mechanical difficulties with parts of the experimental apparatus have prevented the development of a satisfactory conclusion based on results obtained thus far. Recommendations are provided for necessary modifications before further experiments are performed. When these changes are implemented, a final run can be made to complete the analysis. 19 references, 10 figures