Directionally Controlled Hydraulic Energy Effectively Cleans Downhole Perforations

Abstract

This paper was prepared for the 44th Annual California Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in San Francisco, Calif., April 4–5, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The material that plugged slotted perforations in recovered liners was carefully analyzed perforations in recovered liners was carefully analyzed and identified as being mostly formation fines which had been cemented in place by scale and corrosion products. Chemicals would clean the liner surface to bare metal but would not effectively remove the material in the slots. The efficiency of various liner perforation cleaning methods were compared in the laboratory and in situ in producing wells. A new technique using directionally controlled hydraulic energy is described and the critical parameters are defined. This new process has been used to open a high percentage of the perforations prior to the percentage of the perforations prior to the application of non-directional hydraulic, chemical, mechanical or sonic energy behind the liner to effectively clean plugged gravel packs and formations. Field applications are illustrated which show significant increases in oil production after plugged perforations have been effectively cleaned. The seriousness of the liner perforation plugging problem in California's low perforation plugging problem in California's low gravity oil wells was indicated when a study of the impression packer runs in 67 wells revealed that 73% of the wells had less than 50%. of the liner perforations open. perforations open Introduction One of the most important factors to consider in completing a well is the selection of the proper downhole perforations that will allow proper downhole perforations that will allow fluid to freely enter the well bore and at the same time exclude the entry of solid formation materials, particularly where the productive formations are fine grained unconsolidated sands. Milled slot perforations sized to effectively filter out formation solids tend to become clogged or plugged as dirty fluids continue to pass through them. (Fig. 1A) When this occurs pass through them. (Fig. 1A) When this occurs the fluid flow is either restricted or it has to pass through fewer slots at greater velocity. pass through fewer slots at greater velocity. This tends to cause the remaining open perforations to become enlarged due to the corrosion perforations to become enlarged due to the corrosion and/or erosion processes. (Fig. 1B) Coberly showed that the use of undercut milled slots reduced the tendency for the perforations to clog with solids. There has been a perforations to clog with solids. There has been a trend for at least the last decade to almost exclusively use straight cut rather than undercut milled slots because they are approximately $2.00/foot less costly to machine. Unfortunately, the straight cut perforations are more difficult to clean because they clog or plug more completely than do the undercut perforations. The maintenance of open perforations is an absolute necessity if fluid is to be economically produced from or injected into a well bore. produced from or injected into a well bore. Therefore, an effort has been made to better understand the nature of plugging material, effectiveness of available downhole cleaning methods and to develop better methods of unplugging slatted perforations and determining the nature of the well bore conditions before and after various cleaning operations.