Analysis and Design Method for Particulate Diversion in Carbonate Acidizing
Authors
Reza Safari (Weatherford) | Mojtaba P. Shahri (Weatherford) | Clayton Smith (Weatherford) | Francisco Fragachan (Weatherford)
Publisher
SPE - Society of Petroleum Engineers
Publication Date
October 4, 2017
Source
SPE Eastern Regional Meeting, 4-6 October , Lexington, Kentucky, USA
Paper ID
SPE-187525-MS
Abstract
In this paper, an integrated analysis and design method is presented to understand and quantify the effect of particle jamming near the entrance of perforation/wormhole tunnel. An advanced wellbore-scale three dimensional numerical studies with a coupled computational fluid dynamics (CFD) and discrete element model (DEM) were performed to simulate different mechanisms involved in particulate diversion. The results of wellbore-scale simulation were translated into an engineering particulate diversion model, based on the proven diversion mechanisms from laboratory and simulation. The model is incorporated into an integrated carbonate acidizing simulator.
Generally particulate diversion is not used in carbonate acidizing because of the formation of the wormholes and potential difficulty in removing particles from the induced wormholes or perforation tunnel. The new degradable particulate system addresses the issue and presents an efficient approach to divert acid in carbonate stimulation. Detailed physics based simulation demonstrate that the induced wormholes or perforation would plug thru two distinct mechanisms: (1) temporarily seal the entrance of small scale wormholes or perforation with a combination of small and large particles, and/or (2) large particles bridge along tapered path of wormhole/perforation and forms a temporary filter cake on the mouth of opening. Either of these diversion mechanisms will decrease the injectivity locally and promote fluid diversion from inside of well into other normally under-stimulated locations.
The integrated simulator is used to optimize acid stimulation of a vertical wellbore and explain the impact of operational parameters and subsurface conditions on the stimulation efficiency. The model results showed that most optimized bullheaded treatment can be significantly improved by utilizing the particulate diversion system. It is shown that that the developed skin from jammed particulate provided considerable diversion. The results also demonstrated the relation between treatment pressure, the quality of diversion, and subsurface conditions (e.g. permeability, porosity, reservoir pressure and temperature).