oa Petrophysical Properties Evaluation of Tight Gas Sand Reservoirs Using Integrated Data of NMR, Density Logs and Scal

Many tight formations are extremely complex, producing from multiple layers with different<br>permeability that is often enhanced by natural fracturing. The complicity of these reservoirs is<br>attributed to a) Low porosity and low permeability reservoir and b) The presence of certain clay<br>minerals like illite, kaolin and micas in poress. Evaluation of tight gas sand reservoirs represents<br>difficult problems. Determination of petrophysical properties using only conventional logs very<br>complicated. Nuclear magnetic resonance (NMR) logs differ from conventional neutron and density<br>porosity logs, NMR signal amplitude provides detailed porosity free from lithology effects and<br>radioactive sources and relaxation times give other petrophysical parameters such as permeability,<br>capillary pressure, the distribution of pore sizes and hydrocarbon identification. Using of NMR in<br>individual bases or in combination with density log and SCAL data provide better determination of<br>petrophysical properties of s tight gas sand reservoirs.<br>This paper concentrates on determination of three petrophysical parameters of tight gas sand<br>reservoirs: First, Determination of detailed NMR porosity in combination with density porosity,DMR. It<br>is found that DMR porosity method is a gas corrected porosity, and independent facies porosity model,<br>Second NMR permeability, KBGMR; it is based on the dynamic concept of gas movement and bulk gas<br>volume in the invaded zone. It is concluded that KBGMR is facies independent technique and this is the<br>most important value of this technique and Third Capillary pressure derived from relaxation time T2<br>distribution and then it could be used for formation saturation measurements especially in the<br>transition zone. It is found that the assumptions of capillary pressure approximation from T2<br>distribution can be applied in gas wells as well with some consideration due to gas and mud filtrate effects.