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Application of Elemental Data to Wellbore Placement, Completion, and Production: Examples from the Appalachian Basin, USA


The use of elemental data acquired on vertical pilot holes and horizontal drill cuttings to determine the stratigraphic position of a wellbore post-drill is gaining popularity. Moreover, the use of elemental data acquired “real-time” at the well site to geosteer horizontal wellbores is also gaining interest, especially in those areas where conditions such as low gamma ray character and geologic structure can make the use and interpretation of conventional logging-while drilling gamma ray difficult. In an effort to more accurately geosteer horizontal wells we have employed the use of elemental data derived from energy-dispersive X-ray fluorescence. Elemental data was acquired on vertical pilot holes at one foot intervals on core and five foot intervals on cuttings. This data was used to build a chemostratigraphic profile and zonation of the section of interest. The elemental composition of drill cuttings from the horizontal wellbore collected at ten foot increments were compared to the pilot hole data to determine from which stratigraphic interval the cuttings were derived. Post-drill, these data were manipulated to calculate normative mineral volumes. Further, the mechanical properties of the rock along the wellbore were determined by assigning values for Young's Modulus and Poisson's Ratio to each mineral phase. Ultimately, estimation of maximum compressive stress was determined by applying the mechanical rock properties to the effective normal stress equations. Variations in stress along the wellbore were analyzed to determine the most effective completion strategy such as the application of geometric versus engineered completions. Finally, the data was used to evaluate the necessity for production techniques such as limited draw down to reduce likelihood of, or prolong the onset of proppant embedment.