Well Preparation - Essential to Successful Video Logging

Abstract

Summary Successful down hole video logs begin with proper planning and consideration of potential sources of dirty, opaque fluids and the associated execution of well preparation/clean up methods. Sources of dirty wellbore fluids are identified and techniques for controlling each source are offered including the use of a unique surfactant to repel oil from sticking to the optic view port. Recognition of dirty fluid sources and initiating tactical procedures that work to counteract their effects will ensure the highest probabilities that down hole cameras get the desired results with the least investment of time and resources. Introduction Use of down hole video (DHV) cameras for both time-delayed/single-frame video and real time video is increasing every year. Corporate downsizing has intensified the need for swift and accurate diagnosis of well problems and reservoir analysis since there are fewer resources to accomplish the work. DHV dramatically reduces the time and expense involved with trial and error approaches in diagnosing well problems. With proper preparation, DHV provides excellent graphic video footage in nearly any type of well. The prerequisite for successful video logging is the need for a clear, transparent fluid to see through, ex., clear water, dry gas, or air. When complications result from unfavorable well conditions such as gas or sand entry, opaque fluids result making it difficult to achieve a clear viewing medium. Since opaque fluids prohibit viewing the object(s) of interest, an understanding of the sources and proven ways to deal with them will be of value to those interested in its service. The objective of this paper is to share tactical procedures to employ, both before and during logging, to provide optimum viewing conditions for maximum information from DHV. As the database of experience grows larger in the DHV field, better techniques will develop to improve the likelihood of success in more difficult wells by proper well preparation and countermeasures against dirty fluid sources. Background Acceptance of DHV logs in the oil and gas industry did not come quickly or easily. In its early days, DHV had the stigma of being an expensive, unproven, untested tool. Most people upon being exposed to the concept did not think a camera could see anything down there anyway. The cameras could only be deployed when a rig was on the well because oil, if present even in the smallest quantity, would adhere to the lens and the rig was needed to continuously circulate clean water to keep oil off the lens. A highly specialized lens preparation surfactant, developed in the early 1990s, overcame this problem. The surfactant repels oil, preventing it from adhering to the camera optic port that is in front of the video camera lens. The surfactant broadened the applications and success of DHV so that oil in a well is rarely a problem when video logging. Through the successful use of DHV it has been learned that oil and water tend quickly to separate into their respective phase upon entry into the well. This usually provides a very good viewing area throughout the producing interval. If a continuous phase of oil is encountered, the oil will obscure the view until the camera encounters another continuous phase of clear fluid. Oil is no longer the "death rattle" to video logging it once was. The lens surfactant was a milestone in DHV logging, allowing operators to video idle wells containing a thick pad of oil without the need of a rig. Still, wells with significant surface pressure when shut in, remained a challenge. Video signals operate over a very large bandwidth and need a large coax conductor logging cable to compensate for cable attenuation of the video signal. Deeper wells need longer cables which need larger conductors for the video signal. Therefore a rig would often need to kill the well before logging because of the difficulty associated with pressure control using large diameter logging cables then. P. 297