Flow Profile Evaluation in Producer Wells by Geochemical Studies of Oil and Water and Analysis of Anomalies Associated with Deep Fault Zones

Abstract

Abstract A major problem in the mature oil fields is the accompanying water production and oil production from different layers. Geochemical signals from different formations and sources can be used for identification flow profile. The study of geochemistry by area allows to establish the migration paths and movement of fluids inside the reservoir. This article focuses on the geochemical composition and isotopic geochemistry of brines and oils, as well as the metal content and the use of fingerprinting for oils (biomarker analysis). It allows to determine: the modes of development of reserves in different parts of the field, the distribution of liquid flows. The main tasks are: identification of geochemical anomalous zones and wells, analysis of the water source in return wells, analysis of communication between geochemical data and cumulative oil recovery. The first step involves selecting candidate wells for sampling. Then reservoir fluid samples are taken, and their unique composition is measured through high-precision mass spectrometric studies (ICP-MS), revealing the content of components to billions of fractions. The "oil fingerprinting" method (GC-MS) is used to identify biomarkers in oil composition and conditions of their origin. Using the developed automated algorithm allows identifying the distinctive characteristics of each reservoir and each phase - water and oil. Graphs and maps are plotted based on the distribution of the identified geoindicators. Geochemical survey was carried out by samples of wellhead samples of more than 100 wells, working for carbonate and terrigenous reservoirs. Area maps of changes in the geochemical background of the field have been constructed. The data of the fluid's geochemical composition from the development objects gave the determining of the inflow profile of each phase in the section of the perforated layers and allowed to compare it with the available geophysical field surveys. The identified difference of oils by the coefficient 2nC29/C28+C30 indicates different stages of hydrocarbons inflow into the traps. In the Devonian system the bright anomalies in the geochemical composition of water and oil were discovered, which are associated with faults and wells with record oil production for the last 50 years, where the actual cumulative production exceeds the volume of the originally estimated recoverable oil. Received data was used in the adaptation of the reservoir simulation model.