Monte Carlo Simulation Of Pulsed Neutron Logging In Fractured Carbonate Reservoir

Carbonate reservoir is a kind of important oil and gas reservoir. The reserves incarbonate reservoir account for half of the world’s total reserves of oil and gas. Oil-gas fields in the carbonate rocks generally form large oil-gas fields more easily thanthat in clastic rocks. Carbonate rock strata are widely distributed in our country, andlarge and medium oil–gas fields have been found in carbonate rock strata such asSichuan Basin and Tarim Basin. Fractured carbonate reservoir is a kind of densecarbonate reservoir having the characteristics of low matrix porosity and lowpermeability. Due to the developed structural fractures act as reservoir space for oiland gas and percolation channel, this kind of reservoir can form oil and gas reservoirs.Well logging is an important means of reservoir evaluation. The conventionallogging data usually could not be acquired in fractured carbonate reservoir because ofunexpected borehole condition, such as cavity or collapse caused by the developmentof fracture. Pulsed neutron logging was more and more used in the fractured carbonatereservoir as an evaluation method of casing well. The application of pulsed neutronlogging in fractured carbonate reservoir is restricted and the ability of pulsed neutronlogging to detect fracture and provide reservoir parameters needs further researchbecause carbonate reservoir has the characteristics of the development of fracture andsolution pores, irregular reservoir spatial distribution and strong anisotropy.Monte Carlo method is a kind of random mathematics method widely used innuclear logging because of the unique advantages in simulation of particle movement.In order to study the application of pulsed neutron logging in fractured carbonatereservoir and its ability to identify fractures and quantitative evaluation of the reservoir,theoretical model of carbonate reservoir is trying to set up on the basis of organizingthe pulsed neutron logging data in Tahe oilfield. The influence of fractures in thermal neutron density distribution caused by pulsed neutron source, the ability of pulsedneutron logging to detect fractures and the relationship between pulsed neutronlogging data and reservoir parameters such as porosity and water saturation has beensimulated by Monte Carlo method. The results can provide theoretical foundation forthe application of pulsed neutron logging and quantitative interpretation in carbonatereservoir.The results show that the results simulated by Monte Carlo method are in goodagreement with practical logging data and the laws by numerical computing.