Undoubtedly new technologies drive development of resources plays and have spurred a new stage of exploration in the Western Canadian Sedimentary Basin. Engineering based plays place emphasis on drilling and completion techniques, but achieving desired production benefits substantially from improved understanding of reservoir geometry and mechanics, enhanced modeling of the producing formation and ideal placement of wells within the reservoir and throughut the fairway as a whole.
New technologies that were the engine for development in the last few years vary widely in scope and objective. Horizontal drilling is the framework upon which most technologies are based. Steam Assisted Gravity Drainage (SAGD) combines two horizontal wells, thus building a steam chamber that improves movement of heavy oil. Hydraulic fracturing of horizontal wells in unconventional shale, silt and tight sand reservoirs unlocks gas, oil and liquids production that until recently was not considered possible. Large sand cut production made possible by modern pumps producing from unconsolidated reservoirs (CHOPS) enable recovery factors and decline rates that greatly surpass traditional production rates from cold flow heavy oil reservoirs.
SAGD: Steam Assisted Gravitational Drainage
A significant technological breakthrough for in situ oil sands development was the geometry of wellbores: a pair of wells drilled on top of each other: one close to the bottom of the reservoir (the producer) and one above used for steaming the reservoir (the injector), subsequently building of steam chambers that eventually lead to the heavy oil being washed out of the reservoir and into the producer wellbore.
Additional technologies that are employed include logging while drilling (for optimal producer placement based on resistivity curves) and magnetic ranging (used for fast and efficient placement of the injector well at a set distance from the corresponding producer.
Geologists monitor and interpret azimuthal resistivity (ADR) which helps determine the position of the borehole in relation to stratigraphic or reservoir markers, derived from the geological model. By drilling close to the bottom of the SAGD pay zone, active geosteering ensures that the largest possible volume of bitumen is recovered, and significantly less pay is bypassed.
Monitoring the lithology encountered while drilling injector wells leads to optimal liner slot sizing and blank-versus-slotted liner placement, thus maximizing the efficiency of steam injection and ultimately decreasing the steam to oil ratio.
FRACKING: Hydraulic Fracturing in Unconventional Reservoirs
The emergence of multi-stage hydraulic fracturing in horizontal wells has spurred a new cycle of oil and gas production in North America. It was initially thought of as a mostly engineering driven development technique, however it quickly became apparent that optimal well placement within an unconventional reservoir coupled with an appropriate frac design can lead to substantially increased production levels. The combination of geosteering and fracture stage size and frequency has led to remarkable results in reservoirs composed of shale source rock or tight sands.
The efficiency of a fracture stage has been shown to be determined by its placement in the reservoir. Wellsite geologists help determine the best frac port placement based on the direct lithology observation of drill cuttings (and, complimentary, determine spots where fracs may not propagate, avoiding frac placement in areas where the technology and power would go to waste). Based on real time LWD and MWD data, wellpaths are successfully directed by geosteering geologists to optimal stratigraphic placement within the reservoir.
In addition to targeting specific stratigraphic horizons, geosteering can be tailored to direct the wellpath along drilling sweet spots (where the bit can cut the formation in the most efficient fashion), or target fracturing sweet spots (stratigraphic beds where fracking efficiency is highest). Time and money can be saved by geosteering wells rather than drilling along a preset geometry.
CHOPS: Cold-flow Heavy Oil Production with Sand
The Cold-flow Heavy Oil Production with Sand technique is used in poorly consolidated reservoirs with low mobility heavy oil. In the initial phases of production, up to 30% of the extracted volume consists of sand. Such high solids content would normally inhibit or disable production equipment, but modern progressive cavity bottom-hole pumps and pump to surface pumps effectively mitigate this problem. Larger liner slot sizes and large sand cuts contribute to the creation of “worm holes”, creating new conduits in the reservoir immediately adjacent to the borehole, thus enabling the flow of the viscous, low API oil.
Dimensioning the liner slot size is key to this type of development. A thorough understanding of grain size distribution and sandstone consolidation or cementation throughout the reservoir is of paramount importance. Our wellsite geologists collect representative drill cuttings samples and provide detailed descriptions that document reservoir characteristics. In addition, our petrography teams developed comprehensive grain size examination and analysis techniques, providing the basis for understanding uniformity coefficients and how grain size distribution relates to production levels over the length of a well or over time during production
A particular development was caused by the mechanics of moving large quantities of bitumen produced in the Athabasca Region. Essentially, viscous heavy oil needs to be diluted in order to be efficiently transported by pipeline. Condensate was previously considered an inconvenient by-product, but is now highly valued as a diluent for bitumen, and several pools in Central Alberta and the Montney fairway are being re-developed in the search for condensate which sells at a premium in the current environment. Cardium, Glauconite, Viking and Second White Specs formations in Central Alberta along with the Montney in North-Western and North-Central Alberta are re-drilled in the condensate window, while the liquids rich Duvernay play and other deep shale deposits in central Alberta record a resurgence in exploration.
From its roots as a Wellsite Geology company, Chinook has aligned its expertise with new technology and new exploration initiatives. We were involved with unconventional reservoirs from the inception of such plays as the Horn River and Duvernay, and took part in the implementation of remote geosteering techniques in resource play development.
We lend our expertise to High Temperature / High Pressure (HTHP) reservoirs being currently explored, as well as emerging plays such as the Grosmont, Pekisko and Nordegg.
We have multiple personnel involved in heavy oil development, cold flow as well as SAGD and CSS, from the Peace River Oil Sands to Athabasca and Cold Lake regions. Our petrographers frequently re-visit traditional plays in the search for new facets of reservoir mechanics.
Our consultants contribute to the forward looking implementation of new technologies, generating new efficiencies and ultimately leading to increased production.
© November, 2013, Chinook Consulting Services