Oil and gas operators are targeting increasingly thinner, less accessible hydrocarbon zones. Reaching these sweet spots is now easier with intelligent rotary steerable systems (RSS) capable of drilling complex 3-D wells. Such drilling capabilities are insufficient; however, without advanced logging-while-drilling (LWD) technologies to help steer the bottomhole assembly (BHA) along the precise well path. With the introduction of a suite of LWD "Trak" technologies, Inteq is now able to match intelligent RSS with leading edge LWD technologies for comprehensive real-time formation evaluation and precise well positioning in challenging reservoirs.

Advanced LWD Trak technologies
The company's LWD technologies include TesTrak pressure testing, LithoTrak porosity and SoundTrak acoustic services. Combined with the OnTrak azimuthal gamma ray and DeepTrak resistivity LWD measurements, these technologies provide value to the operator in accurately estimating reserves, positioning wells, reducing non-productive time (NPT) and mitigating drilling hazards. These LWD technologies are integrated with the AutoTrak RSS to allow a thorough approach to pre-job planning, real-time decision-making and post-well analysis to achieve improved formation evaluation and drilling performance.

The porosity log includes:
• Azimuthal imaging data for wellbore placement and positioning;
• Azimuthal Pe available for open fracture identification; and
• Azimuthal caliper measurements for wellbore stability analysis.

From a reservoir navigation perspective, the porosity service provides the drilling team with detailed imaging information about the structural nature of the bed boundaries to confirm or adjust wellpath trajectory. The value of the service can be enhanced through the integration of density and porosity data with azimuthal gamma ray propagation resistivity measurements to allow while-drilling calculation of saturation estimates.
The acoustic service provides compressional and shear wave travel-time in "fast" and "slow" formations. These measurements improve the driller's ability to assess shallow drilling hazards typically encountered in slow formations and large boreholes. Borehole acoustic velocities provide an accurate method for pore pressure prediction and are not sensitive to the formation water salinity and temperature variations. Real-time compressional slowness measurements, in conjunction with resistivity data, can further reduce uncertainty in updating pore pressure models while drilling.
The pressure-testing service delivers real-time formation pressure and mobility data. These measurements can be used to update the geological models in real time with respect to reservoir connectivity, compartmentalization and sealing fault identification. Reservoir engineers can use real-time gradient analysis to identify fluids and contacts for optimized wellbore placement.

LWD answers
When drilling with the AutoTrak RSS, the LWD program can consist of azimuthal gamma ray and propagation resistivity, advanced density, acoustic, and formation pressure as well as extra-deep resistivity measurements. This suite of measurements is used to deliver the following information:
Reservoir structure determination. Real-time gamma ray images. Extra-deep resistivity images, and even higher resolution density images are used for reservoir geometry characterization. The resistivity measurements, together with forward resistivity modeling, provide confidence in the interpretation of shale bodies within the reservoir and further refine the geologic model and improve reserve estimates. Compressional and shear acoustic data are continuously acquired in sand and shale to refine the geophysical model.
Reservoir boundary determination. Formation pressures help determine compartmentalization when crossing shales into potentially different sand bodies. Resistivity measurements can be used in the pre-drilling phase to determine the well position relative to the oil/water contact (OWC). While drilling, real-time gamma ray images are used for determining the direction and steepness of the shale/sand interface and making geosteering corrections.
Reservoir pressure measurement and prediction. Resistivity and acoustic velocity trends are used to estimate pore pressure. Real-time formation pressure measurements enable the drilling team to better calibrate the pore pressure predictions and significantly improve wellsite safety.
Reservoir fluid saturations. Porosity measurements allow real-time quantification of porosity and gas identification to calculate saturations. Resistivity measurements serve as an alternate method for determining fluid saturations.

Well positioning in Grane field
Located in the Norwegian North Sea, the Grane field reservoir consists of massive turbidite sandstones located between Lista Formation shales 5,578 ft (1,700 m) below sea level. The shales often have steep boundaries suggesting a deformational origin associated with injections, folds and faults. The base and top reservoir surfaces display rugged topographies. Despite the shallow depth, the seismic definition and interpretation of the reservoir boundaries are problematic, and several of the encountered shale intervals are difficult to detect on seismic data.
Wells needed to be positioned accurately in the subsurface using reservoir navigation in order to maximize oil recovery. Placing the production wells accurately meant 1) staying horizontal 30 ft (9 m) above the OWC and 2) detecting approaching shales (reservoir boundaries) so that wellpath corrections could avoid or minimize shale intervals in the production and injection wells. Deployment of advanced LWD became attractive in the Grane field to address the simultaneous challenges of drilling hazard mitigation, precise wellbore placement and comprehensive reservoir characterization, especially with the ability to log the hole section in a single drilling run.

Grane field Well A
Well A was planned as a dedicated oil producer to drain oil from the field's thick Heimdal sand (Figure 1). The well was to be landed and drilled
36 ft (11 m) true vertical depth
(TVD) above the initial OWC at
5,791 ft (1,765 m). To support while-drilling and post-well requirements, a thorough data acquisition program in real-time and memory was planned. Comprehensive formation evaluation answers were obtained throughout
the 5,305-ft- (1,617-m-) long reservoir section.
The near-bit gamma ray images and density borehole images were used for structural confirmation and well positioning as well as for post-well image interpretation (Figure 2). The gamma ray and density images were of high resolution and in close agreement. Very clear lithological boundaries were identified below 10,302 ft (3,140 m) and around 10,335 ft (3,150 m). Acoustic compressional and shear data were used with the density data to verify seismic inversion data.
Formation pressures were acquired at 16 depth stations. Acquisition using the optimized test procedure allowed three drawdown-buildup sequences per station in less than 5 minutes per station. All 48 formation pressure points were of good quality. Mobilities measured from 290 milliDarcys/centipoise (mD/cP) to 3,183 mD/cP. As expected for pressure measurements in formations with mobilities in this range, the three formation pressure measurements per station were stable and no other indications of supercharging were observed. The TVD difference in the horizontal section is 8.2 ft (2.5 m) and minor pressure variations were recorded, possibly due to production or a varying gas cap along the well bore. The depletion of initial pressures were recorded and fed back to the reservoir models.
This comprehensive logging was performed while drilling in one single run to total depth (TD). During the drilling of the 5,305-ft- (1,617-m-) long horizontal section, all formation evaluation sensors worked 100% and delivered excellent quality data.

Conclusions
The new services in LWD data acquisition are covering a wide range of technologies that earlier were only available in wireline. In addition to providing standard post well information, data can be utilized in real time during the drilling process to improve well placement, mitigate drilling hazards and earlier formation evaluation.
LWD data acquisition in the Grane field demonstrated that advanced LWD systems can provide value-adding data for comprehensive formation evaluation and petrophysical analysis and that these technologies are capable of operating with high reliability while delivering excellent data quality.
By integrating the drilling and LWD planning processes, formation evaluation, drilling optimization and well placement objectives can be met in challenging horizontal sections. LWD acquisition in a single run minimizes NPT and wells can be put on stream earlier than wells undergoing extensive wireline logging programs.