Mobil demonstrated the use of “controlled screen out” designs in 1973.These screenouts were intentionally caused by lowering the injection rates and simultaneously increasing the proppant concentration to insure a fully packed fracture near wellbore. The procedure was attempted in 13 fields in Colorado, Utah, New Mexico, Arizona, and West Texas. Compared to carefully underdisplaced conventional jobs, the wells that screened out generally provided superior sustained productivity.
The theory concerning the effect of incomplete fracture fill-up at the wellbore on productivity ratio is summarized in this paper. It is pointed out that a positive effort to achieve good propping agent packing at the wellbore can result in a productivity ratio of up to twice that which would productivity ratio of up to twice that which would have been attained if the fracture were allowed to close. Also discussed are present fracture treatment methods and proposed modifications to accomplish better fill-up near the wellbore. Data are presented which indicate to obtain good fracture-to-well communication, fracturing treatments should be designed and performed using a controlled screen-out method, and a means of implementing controlled screen-out treatments is outlined.
Results presented emphasize the importance of complete fracture fill-up near the wellbore. Money spent in increasing fracture conductivity will be wasted unless good fracture-to-well communication is achieved. Techniques to insure that the fracture is filled at the wellbore should be applied in all fracturing treatments except where prohibited by unusual conditions (weak pipe, fracturing under a packer, etc.).
Author(s): John E. Smith, Mobil Oil Corp.
Paper Number: SPE 4677