Prediction of damage radius in water injection wells, through interpretation of well injectivity history for the purpose of planning injection well stimulation
Engineeering Honours Degree 2008
University of Adelaide
Abstract Injectivity decline during waterood projects using sea/produced water is a worldwide phenomenon reported in North Sea, Gulf of Mexico and Campos Basin. Presently the Australian oil industry goes into deep waters where seawater ooding is highly feasible and produced water re-injection is commonly required due to the environmental restrictions on produced water disposal. Due to the expense and issues often associated with well intervention, reliable planning and design of damage removal interventions becomes an important issue. In this paper we discuss injectivity impairment due to capture of injected solid/liquid particles by porous rock and the consequent permeability reduction. Three new theoretical formulae for the damaged zone radius are derived from the analytical model for deep bed ltration and investigated. The formula is applied to calculate the required acid volume to remove the damage around the injector. While chemical and economic issues are not considered in the current approach, the proposed formula gives a correct order of magnitude for required acid volume six field cases analysed show that injections of acid volumes that exceed the proposed value completely remove the damage, while the injection of insucient acid brings only partial injectivity recovery after the stimulation for one investigated eld case. Another application, developed in the paper, is determining the penetration depth for re-perforation of injection wells in order to bypass the damaged zone. The developed method expands to drilling uid invasion, nes migration, sulphate scaling and other deposition formation damage processes around injection and production wells.