The aptly titled “shale revolution” is changing the energy production landscape in North America one resource play at the time. The potent combination of horizontal drilling and multi-stage fracking is unlocking oil and gas reserves around the continent. Faced with dwindling recoverable reserves in mature basins, explorers and producers are using technological advances to extract previously unrecoverable hydrocarbons during previous rounds of exploration and production. The current wave of new approaches in exploration and future development is, in part, due to the the unconventional nature of remaining reserves. One answer to today’s needs is new technology.
A Shift in Geological Supervision
With the changing nature of exploration and development in these mature basins, services offered to the upstream industry by geoscience companies must change as well. When it comes to geological wellsite supervision, the weight is shifting from petrographic observations to more quantifiable analysis of the reservoirs. Unconventional reservoirs can often appear unchanging or unvaried in appearance and petrographic features are often sub-microscopic in scale.
Wellsite geoscientists used to estimate porosity and permeability of a target reservoir, but when it comes to shale and silt, the observations are focusing mainly on mineralogical composition and traces of structural features. At the same time, drilling is largely driven by the geochemical composition and geomechanical properties of the rock, with wells targeting the more friable and organic rich stratigraphic layers that can often relate to fast drilling as well.
For these reasons, geological wellsite supervision is shifting focus from petrographical analyses to the 3G’s: Geosteering, Geochemistry and Geomechanics.
3G: Geosteering, Geochemistry, Geomechanics
XRF and FTIR analysis provide quantitative analysis of drill cuttings and core. Remote geosteering, with an emphasis on the geometry of the reservoir, is becoming the preferred method to orient the lateral sections of horizontal wells in narrow, well defined target corridors.
Petrographic analysis of drill cuttings and core is, of course, very important in the exploration phase. A good wellsite geologist will identify mineralogical trends, estimate even traces of porosity, identify the presence of organic material, fractures and faults. However, when drilling upwards of 12 wells from the same surface location, with spacing as tight as 100 meters or less, it becomes difficult to differentiate rocks based on reflected microscopy alone. It is at this development stage that geochemical analysis provides more insight into subtle lithology changes.
XRF analysis can be deployed in the field during the drilling process to provide near-real-time elemental analysis of the drilled strata. Results are interpreted, and lead to quantitative mineralogical determination and interpretation of geomechanical parameters (brittleness and ductility indicators such as Poisson’s Ratio and Young’s Modulus). The geomechanical mapping of the well can then be used to plan frac stage placement in the most efficient manner. Time is saved and completion costs can decrease when frac stages are placed in optimal position or spacing.
Mud gas is collected in isotubes and the preserved gas sample is analysed in depth. The identified and measured components and isotopes provides detailed fingerprinting of fluid characteristics throughout wells, pads, pools and all the way to regional scale. Mapping reservoir fluids allow operators to pick the most prolific intervals in thick unconventional reservoirs.
Remote geosteering adds a tremendous degree of certainty to stratigraphic interpretation by pinpointing the position of wellpath within centimeters relative to known markers. The geometry, as determined by geosteering procedures, is then integrated with other available parts of a geomodel making the interpretation (and drilling of subsequent wells) that much more precise.
Drilling a well in the sweet spot (most drillable, most fracable, most producible interval) leads to smooth well trajectories, decreased tortuosity, reduced risk of stuck pipe, better hole cleaning and ultimately longer, cheaper, better wells.
Integrated geosteering, well logs, seismic, geomodeling, geochemistry, geomechanics, completions efficiency, production results all contribute to “Big Data” collected at the well and pool level. Analysis of combined data and interpretation has tremendous potential to add to the already impressive tally of efficiencies achieved in the production of unconventional reservoirs.
At Chinook Consulting, we are at the forefront of finding and implementing technological solutions in the oil and gas exploration and development process. We have been actively involved in resource plays since the beginning of trends such as the Horn River, Montney, Cardium and Duvernay. The massive experience acquired in these and other plays allow us to keep up with emerging technologies and technical advances.
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