An Overview of Formation Damage and Well Productivity in Oilfield Operations

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and presentspecific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleum engineering. Summary Almost every field operation is a potential source of damage towell productivity. This paper provides a broad overview of the nature offormation damage problems, how they occur during various oilfield operations, and their effects on well productivity. Diagnosis of formation damage problems has led to the conclusion that formation damage is usually associated with either the movement and bridging offine solids or chemical reactions and thermodynamic considerations. The finesolids may be introduced from wellbore fluids or generated in situ by theinteraction of invading fluids with rock minerals or formation fluids. Control of formation damage requires proper design of treating fluids forchemical compatability and strict quality control of fluid physical andchemical properties during treatment. The use of treating fluid filtration, clean work strings (pipe), and inhibited fluids has been shown to be importantin the control of formation damage during well treatment. Introduction Laboratory and field studies indicate that almost every operation in thefield--drilling, completion, workover, production, and stimulation--is apotential source of damage to well productivity. During the many years when thecost of oil was extremely low, however, productivity damage was largely ignoredand emphasis was placed on minimizing costs rather than maximizingproductivity. Since the advent of the energy crisis and the Arab embargo, prevention of formation damage and maximization of well productivity has takenon added importance, not only for conventional well operations but also fortaking advantage of EOR. In EOR, if the conductivity of injection and producingwells is damaged, sweep efficiencies and recovery factors will be adverselyaffected. The success or failure of an EOR project may depend on the ability toinject planned amounts of special fluids and to produce oil at adequaterates. Because repair of formation damage is usually difficult and costly, thebasic approach should be to prevent damage. To achieve this goal, the entireprocess of drilling, completion, and production needs to be viewed as a whole, including extensive preplanning, execution, and follow-up. Failure to controltreatment or operating procedures and chemicals properly at any stage maynegate the effectiveness of all other well-designed and -executed operations. Severely damaged productivity may result from a single misstep in the path ofwell development. A broad knowledge of how formation damage occurs is the first step inprevention of well damage. Each operation must then be studied in detail. Thispaper takes the first step by reviewing how formation damage occurs and showinghow it affects well productivity in various operations. Relative Importance of Formation Damage First, let us look briefly at the relative importance of the formation condition near the wellbore. Although the drainage radius may be several hundreds of feet, the effective permeability close to the wellbore has adisproportionate effect on well productivity. JPT P. 131^