A reliable, water-carried, resin-coated, gravel-packing system now offers an alternative method for sand control in West Coast wells. Significant improvements in aqueous carrying fluids and epoxy resin formulations allow formation of a strong, highly permeable gravel pack that can be placed behind casing or behind a slotted liner in open hole. The system can also be used to patch holes in damaged gravel packs. This paper patch holes in damaged gravel packs. This paper discusses laboratory development of the system and presents results of various applications of the presents results of various applications of the system.
West Coast wells present special problems in the production of sand and attempts to control it. Pays are normally thick zones, 100 to 1000 ft. Pays are normally thick zones, 100 to 1000 ft. with 30 to 500 ft. of net pay. Formation sand normally has a wide range of grain diameters and formation sampling has been rare, making gravel selection a matter of practical experience rather than a science. The primary method of sand control has been to complete in open hole and gravel pack behind a slotted liner. These are routinely done using low viscosity, low gravel concentration slurries.
The development of a reliable, water-carried, resin-coated, gravel-packing system now offers an alternative method for the control of sand in the West Coast area. Concentrated gravel slurries are packed behind casing which has been perforated, or packed behind casing which has been perforated, or behind a slotted liner in open hole, forming a high-strength, high-permeability gravel filter. This allows well fluids to pass easily, but stops formation sand movement.
Resin-coated gravel packing is also an excellent technique for patching holes in gravel pack liners which have failed because of erosion pack liners which have failed because of erosion or corrosion. This is far more economical than replacing the old liner and performing another gravel pack or running and packing an inner liner. Another application is in water injection wells. These wells are stable as long as fluid is being injected, but when injection is stopped the formation may slough into the wellbore.
In order to perform the most effective gravel pack, it is necessary to obtain a sample of the pack, it is necessary to obtain a sample of the formation sand and select a gravel which will prevent the flow of formation sand through it, yet prevent the flow of formation sand through it, yet have the highest permeability possible. Techniques for sampling formation include recovery by rubber sleeve cores, sidewall cores, bailed samples and samples recovered from surface equipment following sand production. The best of these is rubber sleeve coring because this recovers the formation in a condition similar to its natural state. Recovery by bailing or from surface equipment is usually non-representative because of hydraulic separation of the different grain sizes. Sidewall coring results in grain crushing and also entraps drilling mud and mud filter cake during the coring process. This produces a sample which appears to have more clays and fines than the formation actually contains. Sidewall samples are also very small, limiting the testing which can be accomplished with the sample. Maly and Krueger have presented some excellent work on the value of formation sampling.
Once samples have been obtained, a sieve analysis must be run to determine the correct gravel size. There are many methods which have been developed for sizing gravel.
Generally, these use a plot of cumulative per cent of sand retained on increasingly finer sieves versus the logarithm of the sieve opening in inches. A factor is them multiplied by a certain percentile of the formation size to arrive at the percentile of the formation size to arrive at the gravel which is adequate to control that formation.
