A new approach to the in-situ determination of permeability, permeability anisotropy and lateral continuity of barriers to vertical fluid flow is introduced. The procedure employs a wireline-conveyed inflatable straddle-packer in conjunction with a vertically displaced pressure monitor probe to conduct vertical interference tests in openhole. The relatively large spacing between the packer interval and monitor probe (approximately 5 ft) results in a larger depth of investigation than is currently available with other wireline-conveyed tools. Multiple interference tests may be conducted during a single trip in the well. The method of analysis is illustrated with data acquired in an oil well located in a complex, low-permeability, carbonate reservoir that has been under production for almost 40 years and under waterflood for approximately 30 years. As part of a field management program the operator wished to assess the status of pressure maintenance by means of a pressure survey and to measure the permeability anisotropy for use in subsequent numerical simulation work. Analysis of core data indicated that the permeability anisotropy should be low. Feasibility of the testing procedure was established bearing in mind the restriction that flowrates would have to be limited during the pumping and sampling sequences to keep the test pressure above the bubble point pressure. Computer modelling and automatic parameter estimation techniques were employed to estimate the permeability and permeability anisotropy from the interference test data. Electrical and nuclear logs in conjunction with core photographs provided the means to establish the boundaries of the zones tested and to locate the major lithologic units. For comparison the pressure transients measured in the packer interval were analysed by established well testing methods. Introduction In a recent article Weber and van Geuns stated that, "The key to successful simulation is to recognise and evaluate the key parameters that have a major influence on fluid flow. In many cases this will be the vertical permeability profile. Although it is generally accepted that vertical permeability in a sand unit is almost always significantly lower than thehorizontal permeability, little is usually done to measure realistic vertical permeabilities." -JPT October 1990 Shortly before this article was published a new class of wireline formation testers was introduced that can provide the very information envisaged as useful in the above cited article. P. 665^
TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractIn addition to geological and petrophysical data acquisition during the exploration stage, in-situ fluid analysis provides a wealth of information for the appraisal of new discoveries. A recently introduced wireline sampling tool incorporating a downhole fluid analyzer is capable of analyzing fluid composition in real time at downhole conditions, and of measuring the fluorescence spectra of crude oils. These new measurements provide valuable information necessary for the identification and validation of reservoir structures that define the distribution of fluids in the accumulation. The relevance of high quality fluid data in the early stages of the producing life of the reservoir is widely recognized. We present field results of the application of the new sampling tool in an exploration well, where a composition gradient was detected along a 30m liquid hydrocarbon column grading from a 45API crude on the top to a 33API crude on the bottom. During the sampling of the gas cap, retrograde dew formation was detected identifying the fluid and identifying valid sampling conditions. This new information was used to modify the sampling program. Fluid composition analysis relies on optical absorption methods and is currently capable of providing the mass fraction of three hydrocarbon molecular groups: C1, C2-5 and C6+, and CO2.We perform fluorescence spectroscopy by measuring light emission in the green and red ranges of the spectrum after excitation with blue light. Fluorescence in this range is related to the concentration of polycyclic aromatic hydrocarbons (PAH's) in the crude oil. Using the pump-out module to segregate different fluid phase enhances phase detection with fluorescence.
IntroductionA traditional concept is to formulate permeability as a scalar function of porosity.3,4 If samples are well chosen for uniformity of texture, grain size and mineralogy, a clear relationship can be uefined (Fig. 1). However, texture, grain size and mineralogy are, in general, unknown a priori. Therefore, the scalar concept of permeability is This paper proposes a strategy and methodology for the wireline measurement of permeability. The strategy involves new technology; real-time data acquisition and interpretation in parallel utilizing standard wireline logs, high resolution borehole images and a multiple probe formation tester. As part of the method, we introduce a new interpretation for a multiprobe tool based on simple forward models,2 flow regime identification and pressure-pressure deconvolution. The strategy and method are demonstrated using two field examples.Reference and Illustrations at end of paper.The results of one example indicate that features appearing as permeability barriers at the wellbore may not have large lateral extent and therefore do not act as barriers to vertical flow. The other example shows that the converse may also be true, in that, features which are observed to be thin at the wellbore can have considerable lateral extent and be significant barriers.Application of the method is demonstrated using data obtained from two field tests. In addition to electrical and nuclear logs, electric borehole images were obtained over the intervals of interest. The borehole images were used at the wellsite to identify several potential barriers to vertical flow and to choose the test points for the multiprobe formation tester. Subsequently these intervals were tested to determine the effect of the barriers on vertical communication. Additional multiprobe measurements were made in relatively unstratified zones to allow a comparison. This paper introduces a strategy and methodology for the wire-Hydrocarbon reserves are the principal asset in the petroleum inline measurement of permeability that is consistent with the geolog-dustry and the major means for increasing reserves is shifting from icalstructure observed at the wellbore. The strategy involves new. exploration to improved recovery. The measurement of the variatechnology; real-time data acquisition and interpretation in paral-tion along the wellbore of porosity and water saturation provides lei utilizing high resolution borehole images and a multi probe for-a substantial contribution to oil and gas exploration. To improve mation tester. The multi probe tester differs from its single probe recovery, a detailed characterization of the permeability distribution counterpart in that it has an additional two probes, displaced from would be advantageous. Improved recovery requires better technolthe flowing probe, at which the pressure is monitored. In homoge-ogy for planning drilling, pressure maintenance, and flooding. New neous formations this configuration permits the direct determination answers are required in two specific areas: res...
A model is described that is capable of simulating in detail the time variation of formation pressures measured while drilling, in situations where supercharging is significant. Simulation results illustrate the variation of supercharging pressures with formation permeability, drilling-fluid-filtration properties, and drilling-fluid hydraulics. The model is used to explore how drilling operations influence the levels of supercharging when drilling two formations, widely separated along the well trajectory, and of significantly different permeabilities. The forward-simulation capability presented is believed to be a useful aid to the planning, understanding, and interpretation of formation-pressure measurements while drilling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.