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Results
Characterizing A Turbiditic Reservoir
Daggett, Paul (Pioneer Natural Resources) | Knutson, Craig (Pioneer Natural Resources) | Cook, Robert (Pioneer Natural Resources) | Chemali, Roland (Halliburton) | Quirein, John (Halliburton) | Shokeir, Ramez (Halliburton) | Burinda, Bryan (Halliburton) | Pitcher, Jason (Halliburton)
ABSTRACT: The oil producing horizon subject of this publication includes the hydrocarbon-bearing turbiditic interval. The characterization of this horizon and the assessment of the associated reserves are conducted largely through detailed petrographic analyses of a vertical core traversing the reservoir, with a complete suite of wireline logs in a vertical well and with selected logging-while-drilling (LWD) logs in high angle wells. Horizontal layering in the subject reservoir is evident on core photos and on electrical images obtained with both wireline and LWD logs. The layered structure creates a significant electrical anisotropy with vertical resistivity being several folds larger than horizontal resistivity. The evaluation of the formation is then subdivided into two major steps. First, an accurate determination of both vertical and horizontal resistivity across the interval of interest is conducted from high angle wells. Various inversion methods are compared using advanced wave resistivity technology. Second, the computation of oil saturation in the non-shaly interval is performed, based on electrical anisotropy, using a modified Thomas-Stieber method. A key component of the method lies in the understanding of the intrinsic anisotropy of the interbedded shale laminae. The article compares the various approaches used in this field for determining vertical resistivity and horizontal resistivity. No 3D wireline induction log was run. The best overall results are obtained with advanced LWD sensors run in high angle wells. The computed hydrocarbon content obtained from the modified Thomas-Stieber method is compared to the core results from the nearby vertical well. The agreement between them confirms the overall validity of the measurement and method. INTRODUCTION Several fields of the Colville High, North Slope region of Alaska have been studied during recent decades to gain better petrophysical understanding of the laminated structure of some of the reservoirs. That activity extended along three main avenues.
- Geology > Geological Subdiscipline (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.38)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling (0.40)
- North America > United States > Alaska > North Slope Basin > Umiat-Gubik Area > Torok Formation (0.99)
- North America > United States > Alaska > North Slope Basin > Kuparuk River Field > Kuparuk Field (0.99)
ABSTRACT: In the field of geosteering, azimuthally-sensitive, electromagnetic tools are regarded as one of the major advances in gaining a detailed picture of the formations away from the wellbore. In this area, inversion techniques are commonly deployed to reduce the interpretation overhead for operators and service providers. Inversion processing for distance to boundaries is often regarded as a black-box solution, with uncertainty surrounding the results that bring the validity of the inversion process into question. This paper will present a comparison of a well with well-defined boundaries mapped using conventional and azimuthal-resistivity methods to a completely unconstrained inversion. A further review will be examined by comparing these results to a partially constrained inversion using the same input dataset. The functional differences between the two inversion results and their implications to real-world geosteering operations will also be discussed. Finally, the paper will demonstrate the results of the inversion against the main lateral of a well that was geosteered using azimuthal resistivity and azimuthal density, with a comparison of the results and discussion of the ambiguities of geological interpretation against the inversion results. INTRODUCTION In drilling a well, only limited information regarding the exact nature of the formations is known owing to inaccuracies of remote sensing over large distances (e.g., via seismic or offset well interpretation). As the well is being drilled, logging devices in the drillstring provide valuable information that can continuously improve the geological model of formations. Combined with geosteering, a well path can be adjusted on the fly to a position that optimizes recovery of hydrocarbons (Stockhausen et al. 2008; Pitcher et al. 2011). Until the mid-2000s, logging devices to guide geosteering consisted of non-azimuthal resistivity, gamma ray, and neutron tools, with azimuthal density tools to provide structural control.
- Europe (0.66)
- North America > United States > Texas (0.47)
Abstract On a recent well in the Middle Bakken Dolomite, Williston Basin, North Dakota, an operator struggled to effectively geosteer a horizontal well. The geology, while usually relatively simple, proved to be more complex than anticipated. While drilling, the wellbore was steered out of zone, requiring an open-hole sidetrack. After successfully sidetracking, the well was steered out of zone a second time, requiring a repeat of the sidetrack. At this point, the operator elected to deploy a comprehensive geosteering service, which consisted of an azimuthal resistivity tool, dedicated geosteering software, and associated geosteering personnel. Once the tools were delivered to the rig site, all data was transmitted offsite to the geosteering specialists for analysis in real time. The second side track was successfully drilled to TD with no further sidetracks. This demonstrates the ability to rapidly deploy, on short notice, a fit-for-purpose solution to assist operators in accurately positioning wells in the Middle Bakken with a substantial reduction in cost and risk.
- North America > United States > North Dakota (1.00)
- North America > United States > Montana (1.00)
- North America > Canada (1.00)
- Geology > Geological Subdiscipline (0.96)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.43)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.34)
- North America > United States > South Dakota > Williston Basin > Bakken Shale Formation (0.99)
- North America > United States > Montana > Williston Basin > Elm Coulee Field > Bakken Shale Formation > Middle Bakken Shale Formation (0.99)
- North America > United States > Montana > Williston Basin > Bakken Shale Formation (0.99)
- (3 more...)
Abstract In the search for unconventional shale plays with commercial potential, many operators have properties in petroprovince basins containing wells through potentially productive shale zones. These shales were often encountered as part of exploration or development programs for deeper conventional targets. Often, the overlying shale is known to have had gas or oil shows reported during initial drilling, but little or no additional geological data was acquired at the time. This paper discusses the workflow and method to use the minimal information from these existing wells, and to quantitatively incorporate them into a basin exploration program. The process begins with a single new well, such as a sidetrack from an existing well, which is evaluated with the full array of open hole logging tools. Coring (conventional or sidewall), DFIT tests, and other shale-specific logging tools are performed on this initial well. Pre-existing wells that penetrate the objective shale can also be quantitatively assessed for relevant shale properties by using specialized logging tools, such as a combined through-casing pulsed neutron and sonic tool, to map relevant shale properties. These tools are calibrated to the open hole data to generate a wider distribution of data points containing critical shale properties that can be demonstrated to have a strong relationship with production. After the data acquisition process has been performed, the data are combined with existing seismic and structural information to delineate the best areas for further evaluation. Using modern mapping tools, a basin can be rapidly appraised to identify sweet spots, providing further exploration targets for evaluation drilling. This paper discusses limitations, best practices, workflows, and methods, and includes an example of a European shale evaluation log to demonstrate this exploration technique.
- Europe (0.94)
- North America > United States > Colorado (0.16)
Abstract Current well placement in unconventional shale ranges from simple geometric well placement to a gamut of patternrecognition systems and geosteering with geochemical and geomechanical analyses. The wide diversity of systems used leads to uncertainty in the effectiveness of any strategy, with confusion as to the true value or merit of a particular technique. Often, a well-placement strategy is based on what came before, with little regard as to the complexities or differences between reservoirs. This paper reviews the current common practices used in geosteering in shales, for both gas- and oil-producing reservoirs. A brief history of strategy development is outlined, with comments about its perceived effectiveness and value. Examples of successes and failures are examined to attempt to determine the viability of a particular strategy. Finally, alternative approaches and methodologies are reviewed and examined, with comments about the potential application, benefits, and value.
- North America > United States (1.00)
- Europe (1.00)
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.97)