Formation Gas Quantification in the Z-Field Niger Delta Using Multidetector Pulsed Neutron Well Logging Technology

Abstract

The quest for optimal gas detection and quantification in Niger Delta regions for sustainable energy development necessitates advanced technologies. This paper explores a multidetector pulsed neutron well logging technology with improved formation gas sensitivity for precisely characterizing reservoir fluids and estimating gas saturation in a freshwater environment. This innovative method is applicable to tight porosity and low water salinity formations, which are historically challenging conditions for accurate saturation analysis with conventional pulsed neutron logging applications. This technology encompasses (1) a pulsed neutron generator that creates high-energy neutrons that interact with formation nuclei and create induced gamma rays and (2) three gamma-ray detectors and an electronics system that records induced gamma rays based on the gamma-ray energy level and arrival time. In addition, forward modeling of tool responses is a critical component. Monte Carlo N-Particle (MCNP) modeling simulates the three-detector pulsed neutron tool’s gas-sensitive log responses. The predicted MCNP models are incorporated into the saturation analysis workflow to identify and quantify the formation gas saturation considering reservoir fluid properties, lithologies, well completions, and cement densities. A case study demonstrated the use of multidetector pulsed neutron well logging technology for quantitative formation gas evaluations of cased-off reservoirs in the Z-field Niger Delta. This contributes to the use of gas resources for sustainable energy development in Africa.