Development of an Optimized Formulation for Cleaning Water Injection Wells Drilled With Oil-Based Systems

摘要

It is widely known that formation damage during drilling and completions are of prime concern for production wells. Formation damage impacts in injector wells, however, have not received the same level of detail and understanding. Water injection wells are of major importance in hydrocarbon recovery. Water injection wells are often completed as open holes, therefore, mud cake clean-up and damage removal by production of formation fluids is often performed in order to maximise subsequent water injectivity. In some wells, however, this production phase can be prevented due to surface handling limitations or low reservoir pressure. In most cases, when a well cannot be backflowed for long periods, it is possible to bypass near wellbore damage by exceeding the fracture pressure, but this may strongly affect sweep efficiency and uniform injection. Consequently, it is often necessary to inject water immediately after drilling and completion i.e. no possible production phase. In this case, a complete well clean- is required, including the removal of the majority of mud filter cake components in order to maximise water injectivity. The objective of the present study was to develop a completion fluid formulation, based on a previous breaker technology developed by IFP, that allows complete disruption of the oil based mud cake by coalescence of water droplets and dispersion/dissolution of solids which is also compatible with all drilling and production fluids. The experimental methodology used in this study included several steps: the screening of efficient water based additives for dispersing/dissolving solids, the formulation of water-in-oil emulsions with controlled delayed kinetics of breakage adapted to the planned completion program, the assessment of the formulation compatibility with production fluids and finally the validation of clean-up efficiency with dynamic core filtration tests with a significant injectivity enhancement.