w. Prachner, SPE, retiredSu~mary. Pressure drawdown resulting from production causes compaction of the reservoir formation, which induces axial and radIal loads on the wellbore. Reservoir compaction loads increase during the production life of a well and are greater for deviated wells. Presented here are casing and liner loads at initial and final reservoir pressures for well deviation angles of 0 to 45 0 [0 to 0.79 rad]. IntroductionWhen fluid is produced from a reservoir, a reduction in pore pressure occurs. The pressure reduction is greater near the wellbore and increases with production time and rate. The reduction in pore pressure causes compaction of the formation containing the reservoir fluid, which imposes radial and axial loads on the well.Wellbore loads resulting from reservoir compaction are seldom considered in the design of casings, liners, and gravel-pack screens, yet they can be significant. Radial and axial pressureson wellbore tubulars from reservoir compaction are illustrated in Fig. 1 for a vertical well. For a deviated well, the wellbore is exposed to a radial component of the vertical overburden load, increasing external pressures on tubulars.Determining reservoir compaction loads on wellbore tubulars is not a simple task. Field measurement of reservoir compaction loads is difficult because of the time required for these loads to develop and the difficulty in measuring them. 1 Simple analytic techniqucs for calculating reservoir compaction do not account for all the important variables affecting well loads. A computer model, however, can incorporate the many important variables to obtain realistic predictions of these loads, which is the approach presented in this paper.
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Society of Petroleum Engineers of AIME Symposium on Formation Damage Control, to be held in Houston, Tx., Jan 29–30, 1976. 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 paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal, provided agreement to give proper credit is made. 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 An endeavor is made to identify the major causes of completion damage experienced in high capacity producers with sand control installations, and to quantify their impact on well performance. The Total Skin reflecting the combined effect of all parameters influencing the initial inflow potential was determined parameters influencing the initial inflow potential was determined from flowing build-up surveys and segregated mathematically into the components due to partial penetration and completion damage, respectively. Taking into account the pressure losses in the flow string and assuming damage free completions, the wellhead flowing capacities were then determined theoretically for all nonrestricted producers and compared with the actual wellhead potentials observed producers and compared with the actual wellhead potentials observed in the field. Additionally, the completion efficiencies of all wells investigated were calculated. Of the 28 underream gravel pack completions investigated, only 11 were free from rate restrictions due to the risks of coning and erosive velocities and, therefore, could be allowed to produce at the full flowing potential. These included 7 wells with a combined actual maximum rate of 17800 b/d (i.e., 2.543 b/d/well) lower than the theoretical damage free capacity. Additionally, there was a combined capacity reduction of 9493 b/d (i.e., 1356 b/d/well) ascribable to partial penetration. penetration. The review includes one plastic consolidation with a relatively satisfactory completion efficiency of 32% as compared with an average of 27% for the 28 gravel packed wells. Regarding the effect on productivity of the main causes of completion damage it was found that:A comparatively moderate degree of permeability impairment has a severe effect on inflow performance if it occurs in a partially penetrating completion. penetrating completion.Cement squeezing may result in a serious reduction in productivity. productivity.Skin damage can be eliminated if an invert emulsion free from plugging material is used as a completion fluid.
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