Increasing Oil Production by Improving The Method of Hydrocarbon Zone Determination: A Case Study of Using The Pulse Neutron Logging Application in “B” Field, East Java Eko Prastio Abstract— The purpose of this research is used to provide a formation assessment using a Pulse Netron Logging (PNL) tool that can work in the casing or in the tubing. In the effort of enhancing hydrocarbon recovery, this study is done to apply an improved method of determining thickness of Hydrocarbon Zone (net pay) by using the Pulse Neutron Logging (PNL). This tool is usually used in old wells that have been producing for a long time and the purpose of this tool is to look for potential for unproduced hydrocarbons Pulse Neutron Logging (PNL) is one of Porosity measurements in formation evaluation are intended to measure the hydrogen index found in rock formations. The hydrogen index is defined as the ratio of the concentration of hydrogen atoms per cubic cm of rock to the content of pure water. PNL logs do not measure the actual porosity of rocks, but what is measured is the hydrogen content found in rock pores. And the other word the more porous rocks the more hydrogen content and the higher the hydrogen index. Thus, shale which contains a lot of hydrogen can be interpreted as having high porosity.To anticipate this uncertainty, in practice, porosity interpretation can be done by elaborating log density logging. Cased Hole Logging - Sigma Saturation and Carbon Oxygen, it can be seen that several zones that are still zones of the prospect of Hydrocarbons. This study has shown that the Pulse Neutron Log is able to improve the reading of the net pay, so the Pulse Neutron Log is able to improve the reading of the net pay 20 - 40 % Oil and Gas in formation. Production before before Pulse Neutron Logging (PNL) job is 180 bopd and after Pulse Neutron Logging (PNL) job will increase estimate 220 bopd Index Terms— Pulse Neutron Logging, CarbonSat ——————————  —————————— 1 INTRODUCTION eutron logs are used to distinguish porous formations and determine their porosity. This log detects the presence of hydrogen in the formation. In clean formations the pores have been filled with water or oil, the log neutron reflects porosity filled with fluid. Neutrons are part of an atom that has no charge but its mass is equivalent to a hydrogen nucleus. Neutrons interact with other materials in two ways, namely through collision and absorption. Collision generally occurs at high energy levels and absorption occurs at lower energy levels. The amount of energy lost every time a collision occurs depends on the relative mass of the nucleus that collides with the neutron. The greatest energy loss occurs when neutrons collide with another material that has the same mass as, for example, a hydrogen core. Collisions with heavy nuclei will not slow the rate of neutrons too much. So, the biggest decrease in the number of neutrons returned is determined by how much water content in the rock formation. Within a few microseconds, neutrons that have been slowed through collisions will move spread randomly without losing a lot of energy. The new neutron will stop when captured by the nucleus of atoms such as chlorine, hydrogen, or silicon. In this paper the author wants to provide a formation assessment using a Pulse Netron Logging (PNL) tool that can work in the casing or in the tubing. This tool is usually used in old wells that have been producing for a long time and the purpose of this tool is to look for potential for unproduced hydrocarbons. 2 LITERATURE REVIEW Carbon / Oxygen (Carboxsat) Pulse Neutron is a device for measuring Carbon content in oil and Oxygen in water. When this device captures water, the levels of O atoms will be high and C atoms are low. If this device captures hydrocarbons then C atoms will be high and O atoms will be low. The ratio of carbon and oxygen presented between water and hydrocarbons depends on the salinity of water. In the C / O process this time it is specifically only for oil. When inside a well, this tool will fire at Energy. The energy shot is 14 Mev. From each energy level emitted by Pulse Neutron we will get a ratio of several minerals and atoms C, O, Ca and Si. When we get C, O, Ca and Si from this tool. We can already calculate from the ratio of C/O which we usually call RMT C/O and the ratio of Ca/Si which we usually call LIRI. The ratio of C/O and Ca/Si is used to determine the Saturation of oil obtained by comparing the Porosity of the Open Hole. Neutron Porosity measurements in formation evaluation are intended to measure the hydrogen index found in rock formations. The hydrogen index is defined as the ratio of the N