Look ahead of the bit while drilling: potential impacts and challenges in the McMurray Formation

International audienceThe oil and gas industry, operating and service companies, and academia are actively looking for ways to see ahead of the drillbit while drilling to reduce the risks and costs of the operation and improve the well-placement process. Optimal drilling in the challenging and highly heterogeneous reservoirs, where geological interpretations overlook the high-frequency variations in the rock properties, requires reliable subsurface information from around and ahead of the drillbit. To provide this, we have developed a seismic-while-drilling imaging algorithm based on signal processing, drillstring modeling, and pre-stack wave-equation migration. To extend the visibility ahead-of-the-bit, we use the drillbit as a seismic source and image the changes in acoustic properties of rocks both around and ahead of the drillbit. The common practice is to build a reverse vertical seismic profile (R-VSP) gathers. Here, we use a blind deconvolution algorithm to estimate the drillbit source signature from the data directly. Alternatively, we can estimate such a signature through drillstring modeling and top-drive measurements (i.e., force and velocity). The drillstring dynamics is modeled by using Riemann's invariants and a backstepping approach. Next, we input the estimated source signature to the pre-stack wave-equation depth imaging workflow. Our simulations show that providing drillbit source signature to the pre-stack wave equation depth migration consistently delivers reliable subsurface images around and ahead of the drillbit. The output of our workflow is a high-resolution subsurface image that provides vital information in oil sands reservoirs for placement of steam assisted gravity drainage (SAGD) well pairs. Compared to conventional practices, the proposed methodology images around and ahead of the drillbit enabling interactive decision making and optimal well-placement. The key feature of the presented methodology is that instead of cross-correlating the seismic-while-drilling data with the pilot trace and building R-VSP gathers, we use the estimated drillbit source signature and deliver high-resolution pre-stack depth migrated images. Through numerical modeling, we tested the potential impacts, validity, and challenges of the proposed methodology in drilling horizontal wells in SAGD settings with an emphasis on the McMurray Formation. We further compared the results with the conventional drilling practice. In contrast to existing tools that have limited depth of penetration, interpreting seismic-while-drilling data in real-tim

Reservoir characterization of channel-belt strata, McMurray Formation, northeastern Alberta

The reconstruction of stacked channel-belt strata provides important insights into the heterogeneity that results from fluvial depositional processes over a range of spatial and temporal scales. The Lower Cretaceous McMurray Formation of northeastern Alberta represents one of the world’s most significant bitumen reserves, which is hosted in part, within fluvial strata. An extensive subsurface dataset, including production data, is used in this study to characterize stacked channel-belt deposits and demonstrate the impact of numerous scales of heterogeneity on reservoir quality and performance. Bed- through bar- and channel-belt-scale investigations of the McMurray Formation are numerous, however almost all previous studies have overlooked the impact of vertically stacked meander-belt deposits on heterogeneity delineation and production performance. This is a consequence of the difficulty in readily mapping older channel-belt units, which are partially eroded and unresolvable in seismic data. In this study, the delineation of channel-belt remnants that persist beneath the youngest, seismically-defined fluvial system, is achieved. A novel approach to mapping these units relies on: (1) correlating a recently-refined stratigraphic framework into the study area, and in particular, beneath the well-characterized upper channel-belt strata; (2) fine-scale focus of underlying units to define criteria to distinguish vertically stacked channel-belts, including changes in facies, bioturbation type and intensity, sandstone content, grain size, and dip azimuth of dipping strata, which help to define belt boundaries; and (3) the use of preserved parasequence elevations in combination with sub-Cretaceous unconformity paleotopographic elevations, which help identify restricted areas of potential channel-belt development at each stratigraphic level. We show that heterogeneous boundaries between belts, as well as differing stratigraphic architecture amongst successive channel systems, significantly impacts production performance. It is clear that detailed characterization of stacked channel-belt strata at the outset of a project could have a profound impact on their performance and long-term viability

Look ahead of the bit while drilling: potential impacts and challenges of acoustic seismic-while-drilling in the McMurray Formation

International audienceThe oil and gas industry, operating and service companies, and academia are actively searching for ways to look ahead of the drill bit while drilling to reduce the risks and costs of the operation and improve the well-placement process. Optimal drilling in challenging and highly heterogeneous reservoirs, where geological data cannot adequately constrain high-frequency variations in rock properties, requires reliable subsurface information from around and ahead of the drill bit. To provide this, we have developed a seismic-while-drilling (SWD) imaging algorithm using signal processing, drillstring modeling, and prestack wave-equation migration.To extend the visibility ahead of the bit, we use the drill bit as a seismic source and image the changes in acoustic properties of rocks both around and ahead of the drill bit. The common practice is to build reverse vertical seismic profile (R-VSP) gathers. Here, we use a blind deconvolution algorithm to estimate the drill-bit source signature from the data directly. Alternatively, we can estimate such a signature through drillstring modeling and surface measurements (i.e., hookload and hook speed). The drillstring dynamics are modeled and analyzed using Riemann’s invariants and a backstepping approach in a field-verified model. Next, we enter the estimated source signature into the prestack wave-equation depth-imaging workflow. Our simulations show that providing the drill-bit source signature to the prestack wave-equation depth migration consistently delivers reliable subsurface images around and ahead of the drill bit.The output of our workflow is a high-resolution subsurface image, which is then applied to provide vital information in oil-sands reservoirs for placement of steam-assisted-gravity-drainage (SAGD) well pairs. Compared with conventional practices, the proposed methodology images around and ahead of the drill bit enable interactive decision making and optimal well placement. The key feature of the presented methodology is that instead of cross correlating the SWD data with the pilot trace and building R-VSP gathers, we use the estimated drill-bit source signature and deliver high-resolution prestack depth-migrated images.Through numerical modeling, we tested the potential impacts, validity, and challenges of the proposed methodology in drilling horizontal wells in SAGD settings with an emphasis on the McMurray Formation. We further compared the results with the conventional drilling practice. In contrast to existing tools that have limited depth of penetration, interpreting SWD data in real time confidently maps key target features ahead of the drill bit. This imaging workflow provides sufficient time to precisely control the borehole trajectory and stay within the desired reservoir zone. Accordingly, it mitigates the risk of intersecting mudstone-filled channels and lean zones