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Abstract A circumferential acoustic logging instrument that operates at a radial mode resonance of 120 k.Hz utilizes opposing pairs of acoustic transmitters and receivers mounted on pad assemblies which are pressed against the borehole wall. An important feature of the instrument is a baffle system which effectively minimizes the propagation and reception of the d:l.rect fluid wave. The incorporation of the baffle allows both types of boundary waves I the Rayleigh and the guided fluid wave, to be more easily recognized. At present, the primary application of the Circumferential Acoustilog ® is in the locating of natural fracture systems. When run with an orientation section, the instrument is also capable of determining fracture direction. Canadian field examples are presented which demonstrate the capabilities and effectiveness of circumferential acoustic logs. Introduction The Circumferential Acoustilog (CALog), which incorporates the basic concepts of generating and detecting circumferentially propagated acoustic boundary waves, has already been proven successful in locating vertical or near-vertical fractures in various lithologies in North America, on-and offshore Europe, and Canada. The special instrument design using a multilayered baffle system enhances the recorded Rayleigh and guided fluid waves by eliminating any direct fluid component. Figure 1 demonstrates the usefulness and effectiveness of the baffle system in (a) a water tank, (b) an aluminum fracture, and (c) a carbonate test well. Significant enhancement of the Rayleigh and guided fluid waves is clearly shown. Incorporation of an orientation section into the logging tool string has further expanded the. usefulness of the Circumferential Acoustilog by providing the capability for determining major directional trends of subsurface fracture systems. Basically, this is accomplished by measuring the azimuth, relative bearing. and deviation, with both azimuth and relative bearing referenced to receiver R2. Generally speaking, the fracture direction can be determined to within 90 °. However, as the Circumferential Acoustilog instrument rotates while Logging up the borehole, additional azimuth readings in the fractured zones allow for 3 more precise determination of fracture direction. Also, several repeat runs over the subject interval will further enhance this fracture direction capability. Furthermore, two independent caliper pairs of pads 1 and 3 (transmitters) and pads 2 and 4 (receivers) provide two independent borehole size measurements. Fractured zones are characterized by (1) an indication of thick mudcake buildup, especially in the presence of heavy drilling mud or lost circulation material, or (2) by borehole cross-sectional elongation observed preferentially in the main direction of in-situ fractures and microfracture systems. Such fracture-related "washout/breakout" indications result from "chipping" action during drilling operations in those fractured intervals. The sampling rate of the Circumferential Acoustilog is six samples per foot (or two sample per decimeter) which generates a voluminous amount of data. Acoustic data representing 360 degree coverage of the borehole wall is recorded in four quadrants and plotted in a Variable Density (VDL) format. As an alternative, a signature waveform presentation is also available. While a gamma ray curve is provided for correlation 3rd lithology identification, the dual calipers record the two independent borehole diameter measurements between opposing pads.
Abstract A new full-spectrum gamma-gamma logging instrument, theZ-Densilog, measures bulk density (pb) and thephotoelectric cross section (Pe) and represents a significant advancement overpresent instrumentation of a similar type. Instead of recording count rates inonly a few energy gates, the state-of-the-art downhole electronics transmitsthe entire 256-channel gamma ray energy spectra to the digital surface loggingunit. This facilitates sophisticated data analyses previously not obtainable bystandard techniques. Novel, advanced data analysis methods minimize statistical errors, providereal-time compensation Ear variations in detector gain and crystal resolution, and a "four-dimensional" rib and spine model allow the concur cent but separatecorrection for mud cake density and photoelectric cross section effects. Thisresults in greatly improved bulk density and Per measurements. The present paper reviews the basic concepts of the Z-Densilog and discussesrecent Canadian field experiences in clastic, carbonate, and evaporitesequences. Basic Concepts The Z-Densilog (ZDL) instrument model and the techniques for measuring Formation bulk density (Pb g/cc) and photoelectric cross section(Pe, barns/electron) through the use of full spectrum gamma-gamma cay logginghave been discussed previously (Minette et al., 1985; 1986). Basically theZ-Densilog measures and records the 256-channe1 spectra obtained from the longspace detector and the count rate from the discriminated short space detector.While the short space count rate is obtained utilizing a voltage discriminator, the long space spectrum is recorded using B high-speed (12-bit) analog-to-digital converter (ADC). A custom-built flask protects the electronics fromhigh borehole temperatures for prolonged periods of time. Acquisition of data from these detectors along with gamma ray, compensatedneutron, and caliper data is controlled by a surface computer via the Dresser Atlas WTS (wireline telemetry system) which operates at 120 KB/s. As previously discussed in detail by Minette et al. (1986), the Z-Densilog"full-spectrum" technique offers major advantages over the conventional"few-gate" methods presently in field use. Energy Calibration Employing two radioisotopes with different but Known energy levels, the long Space spectrum can be calibrated. While the external americium source exhibitsa peak energy of 60 keV, the energy level of the internal cesium source peak is660 keV. The cesium source is also used for both real-time recalibration of thespectrum and detector resolution calculations. Based on the measuredscintillation detector resolution data, the real-time compensation of theobserved spectrum allows for the determination of bulk density (Pb)and the photoelectric cross section (Pe), independent of detectorresolution. The phenomenological model by Minette (1983) describes thisinteraction of the initial 660 keV energy level gamma rays with the surroundingmaterial and its eventual measurement by the detector. Photoelectric Cross Section The photoelectric crass section (Pe, b/e) is a function of two parameters, theenergy (E) of the incident photon and the mean atomic number (Z). Decreasingenergy" (E) and higher atomic numbers (Z) significantly influences theph1toe Lectric cross section, such as Pe = f' , Z,E-1.
Log Evaluation And Monitoring Of A Unique Heavy Oil Reservoir Project, Alberta, Canada
Campbell, D. (Petro-Canada) | Ducheck, M. (Dresser Atlas) | Frost, E. (Dresser Petroleum Engineering Services, Dresser Industries, Inc.) | Fertl, W.H. (Dresser Petroleum Engineering Services, Dresser Industries, Inc.)
Abstract Conventional open-hole and cased-hole logs, such as the Continuous Carbon/Oxygen (C/O) log, have been used to evaluate steam displacement and sweep efficiency of aheavy oil recovery project in the McMurray Formation, located in Northeastern Alberta, Canada. Results of this reservoir evaluation and steam drive monitoring are presented based on the study of five field wells. This heavy oil recovery project is unique because the reservoir is produced by means of a horizontal well system in which [he heated oil drains by means of gravity segregation. Introduction The MAISP (Mine Assisted In-Situ Pilot) Project was a joint venture by Petro-Canada, Esso Resources, Cities Service Canada, Husky I and Gulf with Petro-Canada acting as operator. The pilot was located approximately 50 kilometers north of Fort McMurray, Alberta at Syncrude in Canada's Lower Base Camp along the Athabasca River on the Northern corner of Suncor's Oil Sands Lease 86. The initial objective of the pilot was the drilling and completing of three horizontal wells from the underlying limestone up into the lower McMurray Formation which lies uncomfortably on top. This was accomplished by digging a 20 meter deep pit into the limestone at the base of a hill. From there the wells, which were eight meters apart, were drilled and completed to a depth of 310 meters into the race or the hill. (see Fig. 1) Six vertical observation wellswere then drilled at the top of the hill back from the face in a pattern as shown in Figure 2. The wells were numbered 0–1 to 0–6, and they were drilled vertically to a depth or 85 meters which put them about 20 meters into the limestone. The wells were used as temperature monitoring wells. Because of the very low gravity of the oil, 7 ° – 9 ° API, steam was used to heat the reservoir to produce the bitumen from the bottom 15 meters of the lower McMurray Formation. The pilot ran for approximately 16 months and steam injection was shut down in March 1981. In April 1981, eight post steam boreholes were drilled on top of the hill back from the face in a pattern as shown in Figure 2. The wells (B-1 through B-9) were drilled specifically for the purpose of evaluating the reservoir after steaming. B-5 was nor drilled due to surface location problems. All the boreholes had temperature logs run 24 hours after drilling. Two of the boreholes, B-1 and B-4, were logged with a Compensated Neutron/Density combination and were cored. In five of the eight wells, the continuous Carbon/Oxygen log was run. The wells were B-1, B-4, B-6, B-7 and B-B. RESERVOIR DESCRIPTION The McMurray Formation of Lower Cretaceous age is a member of the Mannville Group. The McMurray consists mainly of fine to coarse sand with silt and shale interbedding. It lies unconformally on the Deyonian and is overlain by the Clearwater shales. The McMurray oil sands have a great aerial extent (see Fig. 3) and contain vast quantities of bitumen (as much as 900 billion barrels).
- North America > Canada > Alberta > Census Division No. 16 > Regional Municipality of Wood Buffalo > Fort McMurray (0.25)
- North America > United States > Texas > Dawson County (0.24)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.68)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.47)