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Title: Semianalytical productivity models for perforated completions

Abstract

This paper discusses the effects of various perforation and reservoir parameters on the productivity (or injectivity) of perforated completions. Because of the complex, 3D flow into a spiral system of perforations, productivity analysis of perforated completion is not easily amenable to analytical treatment. This paper presents a semianalytical solution for the estimation of skin in perforated completions. Results are presented for two separate cases: the 2D-plane-flow problem, which is essentially valid at small dimensionless perforation spacings (large perforation penetrations or high perforation shot densities) and the general 3D problem, where the vertical convergent flow into perforations is significant. In these analyses, the wellbore and vertical-flow effects are quantified in terms of pseudoskins obtained by accurate finite-element simulations. The effects of perforation damage and formation anisotropy are also included. The results provide a better understanding of the relative role of various perforation parameters in affecting well productivity. Because they are based on theoretical considerations, the correlations allow reliable estimates of the skin in perforated completions. New relations are provided for estimating productivity of perforated completions with formation permeability damage. Results indicate the importance of angular phasing, in addition to perforation penetration, in overcoming the effects of formation damage on well productivity.

Authors:
;  [1]
  1. (Schlumberger Well Services (US))
Publication Date:
OSTI Identifier:
5873591
Resource Type:
Journal Article
Resource Relation:
Journal Name: SPE (Society of Petroleum Engineers) Production Engineering; (United States); Journal Volume: 6:1
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 42 ENGINEERING; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; OIL WELLS; FLOW MODELS; PRODUCTIVITY; WELL COMPLETION; THREE-DIMENSIONAL CALCULATIONS; ANALYTICAL SOLUTION; FORMATION DAMAGE; PERFORATION; WELL SPACING; MATHEMATICAL MODELS; WELLS; 020300* - Petroleum- Drilling & Production; 420400 - Engineering- Heat Transfer & Fluid Flow; 990200 - Mathematics & Computers

Citation Formats

Karakas, M., and Tariq, S.M. Semianalytical productivity models for perforated completions. United States: N. p., 1991. Web. doi:10.2118/18247-PA.
Karakas, M., & Tariq, S.M. Semianalytical productivity models for perforated completions. United States. doi:10.2118/18247-PA.
Karakas, M., and Tariq, S.M. Fri . "Semianalytical productivity models for perforated completions". United States. doi:10.2118/18247-PA.
@article{osti_5873591,
title = {Semianalytical productivity models for perforated completions},
author = {Karakas, M. and Tariq, S.M.},
abstractNote = {This paper discusses the effects of various perforation and reservoir parameters on the productivity (or injectivity) of perforated completions. Because of the complex, 3D flow into a spiral system of perforations, productivity analysis of perforated completion is not easily amenable to analytical treatment. This paper presents a semianalytical solution for the estimation of skin in perforated completions. Results are presented for two separate cases: the 2D-plane-flow problem, which is essentially valid at small dimensionless perforation spacings (large perforation penetrations or high perforation shot densities) and the general 3D problem, where the vertical convergent flow into perforations is significant. In these analyses, the wellbore and vertical-flow effects are quantified in terms of pseudoskins obtained by accurate finite-element simulations. The effects of perforation damage and formation anisotropy are also included. The results provide a better understanding of the relative role of various perforation parameters in affecting well productivity. Because they are based on theoretical considerations, the correlations allow reliable estimates of the skin in perforated completions. New relations are provided for estimating productivity of perforated completions with formation permeability damage. Results indicate the importance of angular phasing, in addition to perforation penetration, in overcoming the effects of formation damage on well productivity.},
doi = {10.2118/18247-PA},
journal = {SPE (Society of Petroleum Engineers) Production Engineering; (United States)},
number = ,
volume = 6:1,
place = {United States},
year = {Fri Feb 01 00:00:00 EST 1991},
month = {Fri Feb 01 00:00:00 EST 1991}
}
  • Finite-element method (FEM) was used to evaluate the steady-state flow response of the near-wellbore region in the presence of anisotropy, shale laminations, and natural fractures. The relative importance of various geometric perforation parameters under such conditions was also examined. The study indicated that completion efficiency is strongly influenced by common heterogeneities. The variation in productivity is substantial and emphasizes the importance of including a good description of the formation heterogeneities in the design and evaluation of a perforating program. The best description is derived by use of data from all available sources (cores, well tests, and logs). The principal findingsmore » of this study are presented.« less
  • A finite-element program was used to study the influence of shot density, perforation length, phasing angle, formation permeability, formation anisotropy, and turbulence factor on the performance of perforated completions in gas reservoirs. The results indicate that when permeability is low ({lt}10 md), turbulence effects are negligible, and perforation length and phasing angle affect productivity ratio. In an isotropic formations, high shot density ({ge}10 md), turbulence effects are negligible, and perforation length and phasingagle effect productivity ratio. In anisotropic formation, high shot density ({ge}12 shots/ft (39 shots/m)) with deep penetration ({le}15 in (38 cm)) is required for the well to performmore » better than an openhole completion. Turbulence effects can cause up to 75% loss in production in high-permeability formations. The nomograph presented can be used to predict productivity ratios and skin factors in gas reservoirs.« less
  • Production rate limits for perforated casing completions in weak rock formations are estimated for a material obeying a quadratic yield condition. Plastic stresses around a spherical cavity are calculated to determine the well pressure value which precipitates solids production. Elastic solutions for a cylindrical cavity are utilized to place upper and lower bounds on the well pressure value which initiates yielding around a perforated casing. The separate analyses define consistent critical well pressure values for initial yield and solids production as a function of rock properties and in-situ conditions.
  • This study extends and, in most details, corroborates the work of previous investigators in the area of relating productivity ratios to perforations. A more refined model, called the finite-element method, permits a significant advance in the precision of the general solution. The principal findings of this study include (1) corroboration of previous conclusions that perforator penetration is substantially more important than perforation diameter, within practical ranges of values, (2) confirmation that productivity continues to increase with increasing shot density, and (3) an analysis of the effect of angular phasing of successive shots, which, for the first time, compares the phasingsmore » used in real perforating guns. This analysis confirms earlier findings that 90/degree/ phasing is the best of those tested (0, 90, 120, and 180/degree/) but produces more meaningful quantitative comparisons than were available before. 10 refs.« less
  • Two view are presented on methods to adapt engineering concepts developed for vertical wells for use in evaluating horizontal well potential. Methods for calculating the productivity index of horizontal wells and for calculating average permeability in the radial concentration flow area given and compared.