An Overview of Formation Damage (includes associated paper 20014 )

Abstract

Introduction Formation damage has been, and continues to be, a concept that is accepted or rejected on the basis of personal opinions, experiences, and perceived understanding of the process of producing oil and gas. It should be a concern for all oilfield people, whether derrick hands or managers, because it affects the economics of the companies that employ us. A good overview on the subject of formation damage is presented in Ref. 1 Formation damage is a very real problem that must be addressed equally by all departments within a company. It does no good for the drilling department to spend time and money doing the best job possible drilling a water-sensitive zone if the production people dump fresh water down the hole as a kill fluid. Good communication between all departments is imperative to deal with a damage-sensitive zone satisfactorily. In this paper, I relate the concepts and ideas formulated from my work and from communication with other oilfield people. I think that with improved techniques and practices, we will eventually improve the present norm of a 20 to 30% recovery factor achieved at the cost of probably 80 to 90% of the reservoir energy. I hope that recovery factors improve significantly. allowing us to produce 25 to 35% or more on average of the original reserves, depending on economics and on how smart we become. This improvement will require a better understanding of the total chemical and physical picture of the reservoir and its fluids by all industry personnel, not just a few researchers. Another important fact is that no matter what appears to be important, for each phase of the operation, production optimization must not be at the price of safety. The best solution is generally one of some degree of compromise. Because the Middle East nations can produce and transport oil to markets for less than $5/bbl [$32/m3], Western nations must change their thinking and start cooperating, much like the Japanese consortiums, to develop better technologies. If we are to compete effectively with other nations and other energy sources and to remain a viable industry, we must change some of the accepted ideas and be more open with information that is not vital to a company's economic security. I think that the SPE Forum Series events are superior to the traditional technological meetings for information exchange. The healthy exchange of knowledge that takes place in the more informal environment of a forum allows our industry to grow far more rapidly simply because the information is current. This concept must be fostered. I recently requested a literature search for articles that dealt with formation damage. I asked for a brief abstract of each article. The printout I received was an 8 1/2x11-in. [22x 28-cm] book more than 2 in.[5 cm] thick. A tremendous number of good articles have been written on this subject, and any library can organize a similar search. It is impossible to mention each article that pertains to the subject at hand-my apologies. Discussion Formation damage can be caused by either a simple or a complex process involving any one of the phases of producing oil or gas. The dynamics of the drilling process alone is so great that it has to alter adversely the rock's ability to flow fluids. It can be a real test of patience to sort through what has happened to establish a likely cause and to formulate corrective measures. As often as not, the information is sketchy or unavailable. A good example is the case where a potassium-sulfate-based mud system obviously went wrong. With the information that was gathered and knowledge of the area where the well was drilled, the most probable cause of the failure was determined to be that the water hauler looked for the closest water source, which unfortunately was an alkali pond or slough. The very high content of dissolved calcium salts caused a chemical reaction in the mud that prevented the system from functioning as designed. The water sources for drilling and workover fluids are seldom documented, much less analyzed, for desirability, often because the standard forms have no space for this information. JPT P. 780^