New Techniques in Wireline Formation Testing in Tight Reservoirs

Abstract

Abstract Some of the main measurement objectives of wireline formation testing are to obtain data on formation pressures and gradients, fluid types and contacts and formation permeability profiles. Tight reservoirs pose many difficult problems when frying to achieve these objectives. The most notable problem is the supercharging effect which often invalidates reservoir pressures taken by the traditional technique of taking a small volume pretest (< 20 cc's). Another crucial objective is to perform measurements safely and cost effectively. This can be difficult to achieve since pressures in tight reservoirs can often require long periods of time to obtain, thereby increasing the costs of rig time, and the probability of tool sticking. The key to advancing wireline formation pressure testing in tight reservoirs is to understand the fundamental causes of the problems, and to use this knowledge to develop methodologies and tools to solve them. Much progress has been recently been made in many areas. For example, the important mechanisms causing supercharging have been identified, and the associated effects have been successfully reduced or eliminated by recently developed methodologies and tools. This paper discusses the problems of wireline formation testing in tight reservoirs, presents recently developed solutions to these problems and shows examples of where they have been applied. The major portion of the discussion will be devoted to supercharging. However, brief consideration will be given to some of other problems of tight reservoirs. P. 419