Jian-qun Wu, M. AL Wisler, and W. C. Barnett
Teleco Oilfield Services, Inc., Meriden, CT
INTRODUCTION
Naturally formed geological bed boundaries are not necessarily horizontal and may not be perfect planes. A predetermined course of drilling cannot ensure that the well being drilled stays in the producing bed. One of the most important technical issues in horizontal drilling is, therefore, how to detect the bed boundary as early as possible so that the well can stay in the hydrocarbon producing bed.
In this paper, we study the use of 2 MHz dual resistivity readings to detect bed boundaries in horizontal and near horizontal wells. The resistivity tool consists of one transmitter antenna and two receiver antennas. The distances between the transmitter and the near and far receiver antennas are 27.5 and 34.5 inches, respectively. A schematic diagram of the tool is shown in figure 1.
In the following, we first examine the theoretical tool responses when the tool is near a bed boundary at large dip angles. Features that can be used to detect bed boundaries are discussed. Then, two horizontal well logs are analyzed. Qualitative comparisons are made between the model responses and the logs.