With the significant drop in oil price and slowing down of the world economy, one might think many petroleum-related technology items will stall or fade out. Although it may be true for those technologies that are “good to have but not essential,” the oil-economy downturn will not affect the areas where research, development, and application of novel technologies are absolutely necessary for the commercialization of hydrocarbon. When we look at world statistics, we find hydraulic fracturing being used as a key operational technique and enabler in the majority of oil and gas wells to produce them economically with long-term stabilized rates. Any major cut in fracturing or stimulation technology will severely affect world production outlook and, consequently, world energy and therefore is unlikely to happen.
Because of the success achieved through hydraulic fracturing, the industry strives relentlessly to maintain the cutting edge in development of novel and innovative technologies and their field applications. Major progress has been made in well completions to accommodate well-stimulation treatments. These include multistage-fracturing (MSF) completions, both openhole and cased; screen tubulars to prevent proppant and sand flowback; and disintegrating drop-down isolation balls and in-tubing plugs, all of which have contributed to fracturing efficiency and cost-effectiveness. A stimulation item worth mentioning is the energized fracturing processes with liquid carbon dioxide (CO2). If the economics works out, the technology is particularly helpful in treating partially depleted reservoirs where natural flowback after fracturing is difficult. For such reservoirs, when fractured with conventional fluids, nitrogen (N2) -assisted lift is needed for the initial startup, resulting in additional time and expense. Liquid CO2 can eliminate or curtail the use of water and simultaneously provide both the hydrostatic head and the energy to clean and lift the well without N2 intervention.
One main challenge faced in the development of tight and ultratight reservoirs is the ability to fracture the formation and produce at commercial rates. The challenge occurs particularly in deep reservoirs exhibiting high fracture gradients. In openhole MSF, the placement of isolation packers and fracturing ports is important to pump a successful treatment. In plug-and-perforate MSF, the proper location of perforations and clusters is important. In either completion system, if the induced fractures are not initiated in the right place, very high breakdown pressures may be encountered that can exceed completion limitations. On the other hand, when perforations are placed in nonsweet intervals, the production may suffer even when fractures can be induced. Industry statistics have shown that, many times, more than 50% of the perforation clusters are nonproductive because of poor placement of perforations, thereby reducing production efficiency significantly. Therefore, it is absolutely necessary to perform a complete assessment and evaluation—from drilling to production—to ensure well placement; landing point; azimuth; trajectory; and, most importantly, packer and perforation/port locations. A model that fully integrates drilling dynamics, real-time geomechanics, geosteering, completion placement, production forecast, and rate sustainability is an essential tool for successful fracturing operations.
SPE 174026 Impact of Remaining Water in Hydraulic Fractures on Well Productivity—Field Examples From Saudi Arabian Sandstone Reservoirs by Zillur Rahim, Saudi Aramco, et al.
SPE 174060 Application of Microproppant To Enhance Well Production in Unconventional Reservoirs: Laboratory and Field Results by Jeff Dahl, Devon Energy, et al.
SPE 177953 How To USE Hydraulic-Fracture Interference To Improve Unconventional Development by Basak Kurtoglu, Citibank Global Energy, et al.
IPTC 17731 A Rigorous Correlation for Quantification of Skin in Preanalysis of Hydraulic Fracturing by Rizwan Ahmed Khan, King Fahd University of Petroleum and Minerals, et al.
Zillur Rahim, SPE, is a senior petroleum engineering consultant with Saudi Aramco’s Gas Reservoir Management Department. He is responsible for hydraulic-fracturing and well-completions technologies in the Saudi Arabian nonassociated-gas reservoirs. An active member of SPE, Rahim has authored more than 90 technical papers and has participated as cochairperson, session chairperson, technical committee member, discussion leader, and workshop coordinator for various international SPE events. He also serves on the JPT Editorial Committee. Rahim holds a BS degree from the Institut Algérien du Pétrole, Boumerdes, Algeria, and MS and PhD degrees from Texas A&M University, all in petroleum engineering.
Zillur Rahim, SPE, Senior Petroleum Engineering Consultant, Saudi Aramco
26 February 2016
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