Hydraulic Fracturing Techbook 2018

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2 | August 2018 | HYDRAULIC FRACTURING: INTRODUCTION F racking–the new drilling process! Well, "hydraulic fracturing" is most certainly not new (circa 1947) and it is not a drilling process. For more than six decades fracturing has continu- ously increased in importance, an obvious result of the industry tackling bigger challenges with poorer quality formations. The evolution is apparent when comparing a modern treatment to the first fractur- ing job as depicted at right. The trend to poorer for- mations may have reached a zenith (both in terms of reservoir quality and importance of fracturing) in today's challenge of completing/producing nano-D "shale" (unconventional) formations. Particularly, given that many of the active unconventional devel- opments are in "source rock," it would seem the end- of-the-line of poorer and poorer reservoir targets. However, one might start at the beginning, since there are interesting parallels with the early develop- ment of fracturing, and the development of fractur- ing practices in shales. The first commercial fracture treatment was con- ducted on the Pickens No. 1 well in Oklahoma. The treatment used a total of 150 lb of sand, according to Halliburton's "Hydrafrac Treatment Report" of March 29, 1949. By all reports, the treatment was a great success; witness the rapid growth in the use of the new technology as treatments grew from zero to more than 3,000 per month over just four or five years (a paltry number compared to current operations to be sure). However, it might then be noted that circa 1970, about 1/3 of the 500,000 fracturing treatments performed were refractures, mostly pumped to place larger volumes of proppant. There is another note from that 1949 treatment report: "Visual checks showed there was sufficient gel [viscosity] to hold the sand in suspension when dropped on the surface of the gelled crude. Since the gel rate had leveled off, 5 gal of water and 150 lb of sand was added to the gelled crude and pumped into the well." Note, there was no pad. The wellbore fluid, whatever it might have been, formed the pad to create/open the fracture. With 150 lb of proppant perhaps not much pad was needed. However, due to low permeability and very low fluid loss, many unconventional treatments have essentially returned to this practice. That being said, as soon as the pump rate is brought up to the desired level, proppant addition begins. The fluid in the well (generally water) forms the pad to open sufficient width to allow proppant entry into the fracture. Then, proppant settling transforms slurry to clean fluid, thus creating new pad to extend fracture length. Finally, it might be noted that the first "water fractures" were pumped in the 1950s–the Dowell "River Fracs." Fracturing then drifted along, with main empha- sis being on surface/operations considerations. These included better pump trucks, larger volumes, blenders for mixing chemicals/proppant "on-the- fly," a slow change from oil- to water-based fluids, the switch from any sand to Ottawa sand, etc. Appli- cations also slowly declined, primarily related to the decline of drilling activity due to Middle Eastern oil entering the market. However, using up the supply of existing well candidates also contributed. A resurgence in hydraulic fracturing began in the late 1970s with development of a natural gas market in North America. This increased demand for gas (and tax incentives) brought "tight gas" into play. For the first time, hydraulic fracturing became a significant cost parameter, leading to the first significant advances in subsurface understanding of hydraulic fracturing. These included the first fracture models (including the first pseudo-3D and planar 3D models), understanding of proppant entry requirements into the fracture, theories on fracture propagation and height growth, understanding the importance of conductivity (leading to the devel- opment of high-strength proppant) and fracturing pressure analysis. Of course, surface developments How much is old, how much is new and where to now? Hydraulic Fracturing By Michael Smith Contributing Editor

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