A review of diverting is made with primary emphasis on granular diverting agents, and wax-polymer diverting agents in particular. The results of laboratory tests are given. Numerous field tests are reviewed, including we!! production data. Both the laboratory and field tests production data. Both the laboratory and field tests show the wax-polymer agents to be the best of the diverting materials tested. The wax-polymer materials are also oil soluble, which will prevent formation damage.
Designing treatments for the stimulation of low-productivity oil and gas wells by acidizing, hydraulic fracturing, and injecting organic solvents or surface-active chemicals is an important function of the modern petroleum engineer. These well-treating processes are well established today. However, in many cases achieved success ratios leave much to be desired. Analysis of job failures shows that all too frequently failure may be attributed to poor treating-fluid distribution. Failure to effectively divert treating fluids from thief zones results either in no treatment or poor treatment of the producing interval.
Thief zones can result from any number of causes, a principal one being nonhomogeneous formations. Producing principal one being nonhomogeneous formations. Producing formations penetrated by oil and gas wells range from 3 to 3000 feet in thickness. As a rule these zones are profoundly inhomogeneous, discontinuous and variable in profoundly inhomogeneous, discontinuous and variable in permeability, sometimes from centimeter to centimeter. permeability, sometimes from centimeter to centimeter. Fluid flow surveys within wells have shown that production from and injection into permeable zones frequently occur in only 10% to 15% of the productive interval. Besides inhomogeneities, variable flow potentials can also be caused by damage to part of the formation. In view of what is known about formation and perforation damage, this is not too surprising.
Productive formations, particularly sandstone formations, act essentially as filters. We know that filters become plugged with time, and we expect them to become plugged, it would appear reasonable to say that we should similarly expect formation rock to decrease in permeability as large volumes of crude oil and brine permeability as large volumes of crude oil and brine which carry solids are filtered through it into the wellbore.