Oilfield Technology correspondent Gordon Cope, looks at recent and upcoming developments across a broad spectrum of technologies that are driving the industry forward.
Several advances have been made to directional drilling. Steerable mud motors, which use a mud-driven turbine in the BHA, are now being replaced by rotary steerable systems (RSS). There are two distinct RSS types. A push-the-bit tool has a series of pads that rotate with the string and push on the side of the borehole and exert a force in order to deflect the bit in the direction the operator wants to drill. The point-the-bit tool has an electric motor that is offset on the drive shaft. The electric motor rotates in the opposite direction of the drill string, holding the shaft geostationary and keeping the tool face pointed in the desired direction.
The direction of the steerable tool is measured while drilling (MWD), using a directional module that measures inclination and azimuth using triaxial magnetometers and gravity sensors. The system contains a transmitter/receiver to send data uphole through the mud system and receive commands back downhole. Logging while drilling, or LWD, enables the operator to keep the tool in the productive reservoir.
Baker Hughes’ AutoTrak Curve RSS has surpassed the 2 million ft milestone since its launch in 2012. The system can drill vertically, curve through up to 15°/100 ft, and continue on for the horizontal sections in one run, eliminating two trips. The programmable system can make real time adjustments to the steering target while drilling, and a gamma ray detector is integrated into the tool, close to the bit, to allow precise geo-steering. Operators have reported reduced drilling time up to four days and saved operators 60% of the rig time per well.
Drill bits are constantly evolving. Traditional roller cone bits are good for drilling through hard rock, but slow down in softer rocks such as shale. Polycrystalline diamond compact (PDC) bits do well in shale, but break down in hard rock. Baker Hughes recently launched the Kymera hybrid line of bits to handle both lithologies. The new line has roller cones and several PDC arms, and creates smoother drilling, improved torque management and precise steering capabilities. Field experience shows improved drilling rates of up to 62% and extended single-bit run lengths of more than 200%. In applications in inter-bedded formations in western Canada, the bit has performed 60 - 100% faster than competing bits.
Smith Bits released a new generation of PDC bits tailored for unconventional shale plays. A range of specific features was incorporated, including improved body geometry and hydraulic enhancements designed to minimise blade packing, improve cutter cleaning and increase ROP. Customers have reported consistent improvement in drilling performance in the curve and lateral hole sections of shale wells. In the Eagle Ford Shale, a Texas operator drilled the entire lateral section of a well at an average rate of 79 ft/hr compared to median performance of 65 ft/hr, representing a 22% improvement in ROP.
Once a well is drilled and cement-cased, the shale must be stimulated in order for the petroleum to enter the wellbore in economic volumes. The stimulation and completion components of an unconventional well can easily exceed the drilling costs, and much R&D is focused on making the process more efficient and economical.
In a traditional perforation and fracturing completion, a service company lowers a perforation gun to the reservoir interval and sets off explosive charges that create perforations in the casing. The perforation gun is then withdrawn in order to perform the fracturing. On the surface, a large fleet of trucks and pumps is assembled around the wellhead. Water is then mixed with proppant (sand to hold the fractures open) and proprietary chemicals (to reduce viscosity and allow further penetration). The water is then pumped down the hole at high pressure, fracturing the rigid shale reservoir sufficiently to allow large volumes of trapped hydrocarbons to escape.
Halliburton recently adapted production-sleeve technology to the fracturing operation. The RapidFrac system uses a metering process that enables a single ball to open multiple sleeves isolated within an interval by swellable packers. Up to 90 sleeves can be incorporated into any one horizontal completion, ensuring maximised stimulated reservoir volume. In a paired set of test wells in the Bakken, Halliburton was able to cut the fracture time, from four days to two days, and significantly reduce water usage.
Tartan Completions has taken the ball drop and multiple sleeve technology one step further. The Calgary-based company has designed the MultiFrac and Burstpoint system that incorporates a port that bursts open when critical fracture pressure is reached. The liner is lowered into position, and the target reservoir portion isolated with inflatable packers. A ball then sequentially opens the sleeves as pressure rises. The BurstPoint ports have a shear tolerance of +/- 0.2%, so once the rupture point is achieved, they simultaneously burst open and fracture the formation. The system allows an operator to place the fracture to within a few centimetres of the target. It is also approximately 30 - 40% faster than an equivalent plug and perf. Essentially, the system has the potential to enhance production, at less cost.
Navigating the future
Much concern focuses around stimulation through hydraulic fracturing. During a fracturing operation, technicians pump millions of litres of water at high pressure into the reservoir, along with sand proppant and propriety chemicals designed to increase penetration. Critics are worried that the process uses up valuable water resources and injects harmful chemicals that have the potential to pollute groundwater.
As a result of these concerns, several states have enacted legislation restricting hydraulic fracturing. New York temporarily banned fracturing of the prolific Marcellus Shale. Several jurisdictions, including Quebec and France, have instigated blanket bans. Should public sentiment against fracturing grow to the point where bans are widespread, the current revolution sweeping the oil and gas sector could potentially come to an end.
Important innovations are being devised to ensure that hydraulic fracturing can proceed in a safe, benign and sustainable manner. Operators are looking for alternatives to the potable water used for farming and public consumption. In northeast British Columbia, Royal Dutch Shell will use treated wastewater from the Dawson Creek Reclaimed Water treatment facility to provide source water for hydraulic fracturing of the Upper Montney shale.
Aqua-Pure, based in Calgary, Canada, has developed the NOMAD 2000, a mechanical vapour recompression (MVR) evaporator mounted on truck-transportable skids and designed to handle water from gas wells. The US$ 3 million units consist of three, trailer-sized modules; an 11 t pre-treatment module, a 20 t evaporator and a 40 t compressor. The system produces pure water at a rate of 60 gal./min (13 m3/hr).
Chesapeake Energy, one of the largest natural gas producers, is experimenting with fracture fluids composed solely of environmentally benign components. Various mixtures of the 100% green fluids are being field tested in wells throughout the US.
In the longer-term future, R&D is being focused on software developments. Artificial intelligence (AI), where software monitors real time drilling and analyses what is happening in order to forewarn or guide operations, is currently under development, as is real time leveraging, or predictive analytics, in which real time drilling information is compared to case-based knowledge to predict the performance of the system.
Part 1 of this article can be reached here.
Adapted by David Bizley
Read the article online at: https://www.oilfieldtechnology.com/exploration/12122013/technology_to_the_rescue_part_2/