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Koepsell R.,Schlumberger | Han S.Y.,PathFinder | Kok J.,PathFinder | Munari M.,PathFinder | Tollefsen E.,PathFinder
Society of Petroleum Engineers - SPE Americas Unconventional Gas Conference 2011, UGC 2011 | Year: 2011

The Niobrara formation is an increasingly active exploration target in the Denver-Julesburg basin that contains both reservoir rock and source rock. The reservoir rock consists of up to four laterally continuous chalk benches and the source rock is comprised of three organic-rich interbedded shales. Both permeability and porosity in the Niobrara chalk are relatively low and production is expected to be enhanced by natural fractures related to: horst and graben structures, dissolution of evaporite beds, wrench faulting, listric faulting, regional stresses, and pore pressure. To develop the Niobrara formation, horizontal drilling combined with multistage hydraulic fracturing increasingly is used. To enhance reservoir understanding and optimize field recovery, advanced logging-while-drilling (LWD) services are now available for real-time acquisition and transmission of high-resolution electrical images of the borehole, azimuthal gamma ray, and multi depth measurement of formation resistivity. Analysis of this information in real time with high data rate LWD acquisition telemetry allows proactive well-placement decision making by comparing apparent dip of the formation to the borehole trajectory. This is effectively used for maximum reservoir contact of the lateral wellbore in the desired chalk bench. In addition, the analysis of the high-resolution images facilitates fracture identification, fault estimation, and structural analysis for the optimization of stage designs for hydraulic fracturing. This paper will expand the use of LWD with high-resolution image interpretation, formation evaluation, fracture system analysis, and structural analysis for the purpose of drilling better-performing wells through optimized well placement and hydraulic fracturing operations. Copyright 2011, Society of Petroleum Engineers.


Moon B.,British Petroleum | Kok J.,PathFinder | Tollefsen E.,PathFinder | Han S.,PathFinder | And 2 more authors.
World Oil | Year: 2011

Shale gas reservoirs typically exhibit high levels of heterogeneity. They are usually produced with horizontal wells, steered using simple gamma-ray (GR) measurements correlated with vertical pilot wells in an attempt to achieve maximum reservoir exposure. Detailed examination has revealed that steering results for horizontal wells using averaged GR correlation techniques and subsequent structural modeling yield non-unique solutions. This article presents a case study in the Woodford Shale where the conventional process results in at least three different plausible well placement results. Incorporating an azimuthal density image into well placement analysis provides a single unique answer. The article also reviews measurements that indicate that well placement variation can have a large impact on stage-to-stage production.


Zaslavsky M.,Schlumberger | Druskin V.,Schlumberger | Davydycheva S.,Pathfinder | Knizhnerman L.,Schlumberger | And 2 more authors.
Geophysics | Year: 2011

The modeling of the controlled-source electromagnetic (CSEM) and single-well and crosswell electromagnetic (EM) configurations requires fine gridding to take into account the 3D nature of the geometries encountered in these applications that include geological structures with complicated shapes and exhibiting large variations in conductivities such as the seafloor bathymetry, the land topography, and targets with complex geometries and large contrasts in conductivities. Such problems significantly increase the computational cost of the conventional finite-difference (FD) approaches mainly due to the large condition numbers of the corresponding linear systems. To handle these problems, we employ a volume integral equation (IE) approach to arrive at an effective preconditioning operator for our FD solver. We refer to this new hybrid algorithm as the finite-difference integral equation method (FDIE). This FDIE preconditioning operator is divergence free and is based on a magnetic field formulation. Similar to the Lippman-Schwinger IE method, this scheme allows us to use a background elimination approach to reduce the computational domain, resulting in a smaller size stiffness matrix. Furthermore, it yields a linear system whose condition number is close to that of the conventional Lippman-Schwinger IE approach, significantly reducing the condition number of the stiffness matrix of the FD solver. Moreover, the FD framework allows us to substitute convolution operations by the inversion of banded matrices, which significantly reduces the computational cost per iteration of the hybrid method compared to the standard IE approaches. Also, well-established FD homogenization and optimal gridding algorithms make the FDIE more appropriate for the discretization of strongly inhomogeneous media. Some numerical studies are presented to illustrate the accuracy and effectiveness of the presented solver for CSEM, single-well, and crosswell EM applications. © 2011 Society of Exploration Geophysicists.


Alford J.,PathFinder | Tollefsen E.,PathFinder | Kok J.,PathFinder | Han S.Y.,PathFinder | And 3 more authors.
Hart's E and P | Year: 2011

Work on Anadarko Petroleum Corp. operated wells in the active Eagle Ford shale play of South Texas has demonstrated the benefits of using real-time formation evaluation along the lateral to optimize well placement and improve drilling efficiencies, thus improving shale oil and gas economics. It is shown that logging-while-drilling (LWD), when integrated into the bottomhole assembly (BHA) allows real-time formation evaluation that can assess rock properties in detail and therefore expedite accurate well placement. By employing proprietary geosteering software, it was possible to build a 3-D structure property model from the Eagle Ford pilot well's logging data. Employing post-drilling LWD measurements, a modeled interpretation is constructed that shows that the well lands high in the reservoir and consequently excites the reservoir.


Kok J.,Pathfinder | Han S.Y.,Pathfinder | Tollefsen E.,Pathfinder
Proceedings - SPE Annual Technical Conference and Exhibition | Year: 2011

Unconventional shale plays are characterized as low porosity and low matrix permeability reservoirs. In addition, they lack an obvious seal or trap, are of large regional extent, and understood to be heterogeneous in nature. Due to this understanding, vertical, pilot wells are commonly drilled to evaluate rock properties and determine horizontal shale gas targets. Horizontal wells are drilled then completed by means of hydraulic fracturing to maximize reservoir contact and enhance production performance. To position the lateral production borehole within the defined target, geosteering is commonly performed using a single averaged gamma ray measurement. In the initial development phases, this is often perceived as the most economic means for measuring and steering the production hole. However, acquisition of sufficient LWD data demonstrates that by relying on a single measurement, structural models can be made to present several different possible correlation scenarios. Obviously, a non conclusive structural interpretation will negatively impact any efforts of evaluations for efficient field development. While, averaged resistivity measurements may be utilized as an additional correlation reference to complement gamma ray, improvements to correlation accuracy are best achieved with azimuthal images such as density, resistivity or gamma ray images. Real-time image measurements are used identify thin layers while cutting up or down dip as well as structural dip authentication along the well trajectory to provide a high level of confidence in the interpreted geosteering model. Effectively, an accurate structural model is also an effective tool to design completion, correlate formation properties and refine target sizing while providing the foundation for formation evaluations. This paper illustrates how correlations using only an averaged gamma ray measurement for structural modeling and steering of a production hole can result in multiple interpretations. This uncertainty is a potential cause of inconsistent reservoir interpretations and low or varied production across a given field. In comparison, acquiring sufficient measurements while drilling for formation evaluation, and well placement can be applied to deliver consistent production results and provide a common platform for completion design practices. Copyright 2011, Society of Petroleum Engineers.


Kok J.,PathFinder | DeJarnett J.,Anadarko Petroleum Co. | Geary D.,Anadarko Petroleum Co. | Vauter E.,PathFinder
SPE Eastern Regional Meeting | Year: 2011

The Permian Basin of West Texas and New Mexico is a prolific brownfield that produces from numerous clastic and carbonate horizons. Some of these reservoirs are composed of several separate thin tight sands ranging from 6 to 11 feet. Historically, these thin bed formations were bypassed because of lack of production in vertical wells. To economically exploit hydrocarbon reserves from these thin beds, maximum reservoir contact within a single layer or commingled across reservoir layers off a horizontal well path is necessary. To maintain or steer the well within these thin reservoirs, distinct log responses across the reservoir is needed for lateral correlations and well trajectory steering. Unfortunately in the thin reservoir realms such as those encountered in the Permian Basin, a lack of contrast in log measurements, such as gamma ray and resistivity, often results in poor geosteering decisions with the consequence of high costs in well construction. Advances in horizontal and LWD technology now offers real-time placement accuracy using proactive bed boundary mapping technology that incorporates a sophisticated arrangements of resistivity transmitter-receiver arrays. It is well understood in the technical domain that log measurements require a degree of change in formation log response for steering applications. However, in low log measurement contrast reservoirs, deep directional curve measurements are currently the optimum alternative for well positioning interpretation. Copyright 2011, Society of Petroleum Engineers.

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