A Technique To Evaluate Deviated Wells With Standard Logging Tools

Abstract

Escaron, P.C., Schlumberger Well Services Member SPE-AIMEAbstract. A new technique to log highly deviated wells with standard logging tools has been developed. The logging tool is carried at the end of the drillpipe inside a protective sleeve. The logging cable is pumped to the head of the tool where mechanical and electrical connections are made with a special wet makeup connector. The logging tool is extended in the open hole by a rigid stinger and retrieved by the logging cable. Logging takes place during the retrieval. This paper describes the new technique and the special equipment paper describes the new technique and the special equipment required.Introduction. The economic and environmental conditions of the last few years have provided an incentive for increased exploration of new horizons: shallow gas production and drainage production of viscous oil. New restrictions on the number of production platforms in certain locations have been imposed because of navigational or environmental conditions, and these limitations have required extensive use of highly deviated wells. These factors have resulted in an increased number of wells with high deviation ramps. Hole deviations often exceed 70 degrees and ramp lengths could reach 10,000 ft (3048 in).PROBLEM DEFINITION PROBLEM DEFINITION In the past, efforts have been made to improve the success ratio of logging operations using standard logging tools in highly deviated wells which relied only on the force of gravity. These efforts were centered on reducing friction of the tool body and decreasing interference between the tool and the obstacles in the well. Success has been limited because hole conditions are variable and gravity alone at high deviations is often not able to provide sufficient forward motion to overcome all obstacles encountered in the wells.As an alternative, extensive use has been made of pumpdown techniques. In this procedure mud pressure is used to pumpdown techniques. In this procedure mud pressure is used to push logging tools through the drillpipe and out into the push logging tools through the drillpipe and out into the formation. Some tools can log the formation through the drillpipe but others have to be extended into the open hole. There are several drawbacks to this approach. The 2 3/4-in.-diameter restriction for the tools often results in a response of lower quality than that of the larger standard tools. Many services are not available in the smaller size. Also, it was found that some heavy-weight drillpipe has restrictions lower than 2 3/4-in. inside diameters.Frequently, logging operations in highly deviated wells led to costly and sometimes futile attempts which, at best, delivered a lower quality product.ALTERNATIVE APPROACHES. Various methods were considered which would allow logging with standard tools. Propulsion systems based on hydraulic or electromechanical devices were found to be complex or slow. Their reliability, bulk, and cost raised more questions. Cableless systems involving downhole memorization of the logging information were also considered, but present technology is not adequate to meet the memory requirements.Experience indicates that most deviated wells are typically production wells targeted at a few intervals of limited length.Method Description. It is clear that the most reliable way to transport the tool to the interval of interest is by means of the drillpipe which makes the hole. Such a system was conceived and developed.