Adsorption and Distribution Challenges of Commingled Cyclic Steam Injection - Sudanese Oil Fields

Abstract

Thermal Enhanced Oil Recovery (TEOR) is a family of tertiary processes defined as “any process in which heat is introduced intentionally into a subsurface accumulation of organic compounds for the purpose of recovering fuels through wells”. After hot water and heated gasses have been tried, the most common and effective vehicle used to inject heat is saturated steam. Most of commingle thermal wells has a problem in steam intensity distribution among the layers, which will lead to inconsistency in steam adsorption and some layers would adsorb more than double of the designed steam injected volume. This phenomenon will lead to low productivity and negatively impact the distribution of water cut in different layers. Steam adsorption and distribution represent one of the main challenges of heavy oil production from Sudanese oil fields. Very limited studies have been conducted in this field in Sudan oil fields, and this study is focused on addressing this challenge to maximize recovery factor for each well and each field. In this study the challenge facing Bentiu reservoir in Fula North East (FNE) and the Bamboo fields that are located in heavy oil zone with target of production around 85% of the total reserves will be highlighted. These fields are of shallow depth ranging between 520m and 1300m and rather low pressure gradient 1.09 psi/m, and with reservoir temperature around 44 Co and 65 Co respectively. The studies report our investigation on the benefits of steam adsorption to enhance the oil recovery focusing on the distribution of the steam inside the layers. Our ultimate goal is to design an optimum steam injection protocol that will maximize the recovery factor for these oil zones. The study covers analyzing and reviewing the actual steam intensity distribution among each layer in the two fields that are later compared with the designed ones. In a later stage, a pilot model has been designed using advanced thermal EOR Simulator to understand the effect of commingle injection and production (Steam adsorption and distribution) using data from single layer. The results showed that the production performance of the wells has been improved and the cumulative oil production increased almost five times compared to last cycle. Also the cycle duration has been extended for more than two years, and a new computer model has been developed to calculate and interpretate the surface steam injection parameters from boiler to wellbore and reservoir Parameters (Steam Injection Testing Interpretation (SITI).