Volumetric Reservoir Estimation of Nandpur Gas Field

Abstract

The present study pertains to the modeling of the productive zones from seismic and well log data. This was carried out by using seismic lines, 0-845-KBR-42, 0-845-KBR-43, 0- 845-KBR-38, 0-845-KBR-39 and well log data of Nandpur-09 provided by the Directorate General of Petroleum Concession. The area is important for its hydrocarbon (Oil & gas) structural traps. The Nandpur Gas field was acquired by OGDCL. The area lies in the Middle Indus basin and the two reservoirs are encountered during the study of well Nandpur-09 are Lumshiwal and Samana Suk Formations. The present study area is the Nandpur Gas field which is situated at a distance of 64 km near Distt. Multan. The field was discovered in 1984 by OGDCL as the first (and so far only) gas field of the Punjab platform. The gas, which has accumulated in different Cretaceous and Jurassic formations, has a very high Nitrogen gas (N2) content. During the study of Seismic sections first of all we pick a prominent reflector from the seismic sections. In the interpretation of the present study two reflectors were marked at different times R1(Lumshiwal Formation) at 1.3 sec as R2(Samana Suk Formation) was marked at 1.5 sec then note the time of each reflector against the shot. Moreover, we have done manual preparation of the time and depth contour map of the Lumshiwal and Samana Suk formations on the base map. The formula used for the conversion of time into depth is given below:

S = V*T/2

Then we calculate the area of each reflector from the depth contour map is placed on graph paper and calculate the no. of boxes of 1cm * 1cm. So with the help of this work, we come to calculate the Reservoir area of each reflector by utilization of depth contour maps. In Petrophysical studies first of all we identify Reservoir zones and determine Reservoir parameters that are Volume of Shale, Porosity(Density* NPHI or Sonic), Net Pay calculation after application of cut-off, Resistivity of Water, Water Saturation, Hydrocarbon Saturation, Lithology(Mineral Identification). During petrophysical interpretation, different cross plots were constructed like porosity, volume of shale, Hydrocarbon saturation, and Water Saturation against depth interval which shows the behavior of the reservoir which is the key interest zone. Volumetric reserves are found by using the reservoir estimation Formula. The reservoir quality of the Lumshiwal and Samana Suk Formation was much better in terms of clean Sandstone, porosity, water saturation, and permeability.