PROVIDING HIGH-QUALITY DENSITY MEASUREMENTS AND FORMATION IMAGES
Sperry Drilling, a Halliburton (NYSE: HAL) business, today announced the release of the 9-1/2-inch Azimuthal Lithodensity (ALD?) service, providing real-time density measurements and images in boreholes up to 17-1/2 inches. With this addition, Halliburton offers the greatest range of hole-size capability and is the only service company to provide this larger wellbore measurement.
ALD provides downhole density measurements, including high-quality borehole image logs, to help optimize wellbore placement through geosteering and to reduce geological uncertainties. The measurements, delivered via LWD, also eliminate costly wireline conveyance runs and capture data immediately after drilling when the borehole is in the best condition.
The 9-1/2-inch ALD provides the same functionality as its smaller counterparts, including azimuthal density, and photoelectric and acoustic stand-off measurements. This information has a wide range of applications that can help determine a formation’s porosity, rock strength, pore pressure and borehole geometry.
“ALD addresses an important market need and is currently the only commercially available LWD density service designed for large-diameter boreholes,” said Corey Walker, vice president of Sperry Drilling. “In areas like the Gulf of Mexico and other regions where large boreholes are common, we are well positioned to meet increasing demand.”
In the Gulf of Mexico, ALD has demonstrated value to operators. In one case, an operator used the density measurement to identify shallow hydrocarbon deposits in a 17-1/2-inch borehole. In another case, an operator used borehole density images in real-time to determine the formation dip and reservoir structure immediately below a massive salt interval in a 16-1/2-inch borehole, where surface seismic data was poor.
Previously, operators had to perform wireline runs to retrieve these results, but ALD provided this information without adding expensive deepwater rig time, operation costs and risks associated with wireline conveyance.
The ALD? service provides fit-for-purpose, reliable measurements that are suitable for a wide range of petrophysical and geological applications. The service not only provides accurate density and Pe logs for reservoir evaluation, but also provides high-quality borehole images for structural dip interpretation, geosteering, and hole stability applications. As the ALD tool rotates, the density, Pe, and acoustic standoff data are acquired in 16 azimuthally oriented sectors or bins, referenced to either the high side of the borehole or magnetic north. The azimuthal data can be presented as conventional log curves (top, right, bottom, and left quadrants) and as borehole image logs. Azimuthal density curves and image data are also available in real time.
ALD image logs reveal borehole shape features such as hole spiraling and stress-induced breakout. In addition to the density and Pe image data, an acoustic standoff sensor, mounted in line with the scintillation detectors in the 6-3/4-, 8-, and 9-1/2- in. ALD tools, provides direct measurements of standoff, borehole diameter, and borehole geometry, for better evaluation of log and borehole quality.
The ALD service features a proven rapid-sampling statistical technique for optimizing density and Pe data quality. This technique identifies and segregates the highest-quality count-rate samples acquired with minimum standoff, and operates even in vertical wells where high-side azimuthal binning is not possible.
ALD? SERVICE APPLICATIONS
- Accurate density and Pe logs, even in enlarged boreholes or with bi-center bits
- Formation imaging for:
? ? ? ? ? ? ? ? ? ?– Geosteering;
? ? ? ? ? ? ? ? ? ?– Structural dip in high-angle wells;
? ? ? ? ? ? ? ? ? – Borehole breakout, washout, and spiraling.
- Porosity;
- Lithology;
- Pore pressure;
- Gas detection (with CTN? neutron porosity tool);
- Formation mechanical and seismic properties (with the QBAT? or XBAT? sonic tools).
ALD? SERVICE FEATURES
- The first and only LWD density service for larger borehole sizes;
- Azimuthally oriented density, Pe, and acoustic standoff measurements;
- Rugged detectors and electronics for greater reliability;
- Real-time formation imaging in oil-based and water-based mud systems;
- Three independent techniques for optimizing density and Pe log quality:
? – Azimuthal imaging;
? – Rapid sampling;
? – Conventional.
- Operates in SOLAR? conditions of up to 175°C / 347°F and 30,000 psi / 207 MPa on certain sizes
ALD? SERVICE BENEFITS
Reduces cost and time by eliminating wireline conveyance even in SOLAR conditions;
Optimizes wellbore placement through geosteering;
Reduces geological uncertainty and refines the earth model by measuring structural dip in real time.
Applications
Case1:ALD? Sensor Provides High-QualityFormation Density Measurements in Challenging Low-Angle, Bi-Center Wellbore Location: Gulf of Mexico
Operator’s Challenge
The anticipation of possible wellbore instability issues led an operator to employ a formation evaluation program that relied heavily upon logging-while-drilling (LWD) data. The potential for hole deterioration over time would make wireline operations risky and could result in no logging data at all. The operator required an LWD triple combo with density porosity and thermal neutron sensors to drill and log the interval.
Halliburton’s Solution
For optimum density measurements, detector contact with the wellbore is critical. In this 12-1/4-inch x 14-3/4-inch bi-center hole, with a maximum inclination of only 30°, there was a high probability of the tool string moving away from the borehole wall when rotated in the oversized hole. Furthermore, the high 14-ppg mud weight reduced the density contrast between the formation and the annulus, rendering density contrast binning as an ineffective means for measuring true formation density. Azimuthally-binned density measurements from Sperry Drilling Services’ ALD? azimuthal lithodensity sensor provided the best method for obtaining accurate density measurements. Because the measurements can be grouped together, or “binned”, according to the direction the detectors are facing, the measurements acquired when the sensor was closest to the borehole wall could be trusted to provide accurate values of porosity.
Economic Value Created
The customer used Sperry’s ALD sensor and CTN? compensated thermal neutron sensors when drilling the 12-1/4-inch by 14-3/4-inch hole section, and had an excellent triple combo evaluation of the interval. For sections with corresponding wireline data, the LWD triple combo data was compared to the wireline data, revealing virtually perfect agreement. The ALD sensor imaging capabilities resulted in striking images of structures that intersected the wellbore, which provided for determination of dip direction and magnitude.
Case2:ALD? Sensor Saves Operator $70,000 by Replacing Wireline Location: Gulf of Mexico
Operator’s Challenge
An operator wanted to be certain that LWD density data were equivalent in quality to the data provided by wireline tools.
Halliburton’s Solution
Sperry Drilling Services recommended running the ALD sensor in a section of the well. The ALD sensor provides early and accurate azimuthally-oriented density, Pe and standoff measurements. The customer planned to run a wireline tool over the same interval to verify the LWD density data.
Economic Value Created
The ALD sensor and wireline data were virtually identical, which reassured the operator that the ALD sensor yielded valid data. The total economic value created was $70,000, based on eliminating the cost of additional wireline services.
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