Abstract

Dipmeter is a traditional wireline logging tool that is proved to be very useful in hydrocarbon exploration. The introduction of microresistivity imaging tools made dipmeter almost obsolete. But dipmeter studies are useful even today since most of the old wells contain only dipmeter data and not imaging data. Also, the acquisition cost of dipmeter data is low. Present paper describes a field study using dipmeter data. In this particular field, called Field-A, only dipmeter data is available. The study was focused mainly on Sand-A, which is gas-bearing in some areas. First, structural dips were analysed. The structural dips in the coal-shale sequence below Sand-A are in the range of 20 degrees mostly towards NW and some towards SW. The structural dips of shales within Sand-A are 8 to 10 degrees in magnitude. The azimuth is NW in some wells, SW in some others and SE in a few wells. It was observed that the wells having westward dips (NW or SW) are hydrocarbon bearing and wells having SE dips are water-bearing. The structural dips in the formations above Sand-A are about 8 degrees with azimuths similar to shales within SandA. From the analysis of stratigraphic dips, it was observed that the main paleocurrent direction for Sand-A is towards NW. Thus the likely source for hydrocarbons will be towards NW of the area under study. From this, it may be concluded that local highs in the structure towards NW will be the prospective traps for the hydrocarbon accumulation. In the eastern direction, drilling may be restricted to area bounded by a possible fault upto which the structural dip is towards west. Thus, dipmeter studies help in identifying prospective areas and ruling out unfavourable areas.