This paper was prepared for presentation at the SPE International Meeting on Petroleum Engineering held in Beijing, China, 24-27 March 1992.However, it was first presented at the 1991 Offshore Europe Conference, held in Aberdeen, United Kingdom, 3-6 September 1991.
Numerous additives and fluid systems have been introduced to the oil industry for the control of fluid loss or to provide a nonmechanical means to isolate intervals. Most are either viscosified fluids and/or solid particulates. There are advantages and disadvantages to both types. Recent testing has shown many systems to be quite damaging to the intervals they are to protect, especially in control of high differential pressures.
Research performed over the last few years has led to the development of a novel fluid loss control agent that is capable of controlling fluid loss without imposing severe permeability damage on a potential producing formation. Laboratory tests have shown the material to be much less damaging than particulate systems, such as graded salt slurries, and capable of particulate systems, such as graded salt slurries, and capable of holding higher differential pressures than simple gelled brines. Regained permeability values have been as high as 100%. Typical regain permeability values are around 90%compared to much less for other systems tested. The fluid system can be prepared from most brine solutions and weight adjusted to prepared from most brine solutions and weight adjusted to match densities of fluids in the wellbore.
The term fluid loss control material (FLM) is used widely in the oil and gas industry to describe several products used in various applications connected with the completion, stimulation, and workover of a well. For this paper a fluid loss control treatment (FLCT) will be defined as the use of a FLM in the near wellbore region to prevent fluid loss to the formation, and functioning in a static state. This will differentiate the term from those FLM products used to limit fluid loss while drilling, cementing, or stimulating a well where the product is continuously functioning during the operation, i.e. dynamically. Many of the materials called FLM are applicable to both situations.
FLCT have a number of applications in all phases of a well completion and maintenance. The most routine uses are in the completion of a well and in workover. In completion work the FLCT are routinely applied after perforation of high pressure zones where a weighted completion fluid must be restricted from entering the newly exposed formation. For wells that are gravel packed, some gel based FLCT are often used to provide formation support while tripping the perforating guns out and the screen assembly in. They may be used again toprovide fluid loss control when tripping the gravel pack service tool out and a production packer in.
The use of FLCT in workovers is limited only by the imagination of the operator. Some common uses are as kill pills and for zonal isolation. The latter would be used in conjunction with such treatments as acidizing, fracturing, water control, and the repair of casing leaks.