Investigation on the Benefits of Steam Adsorption and Distribution during Cyclic Steam Injection to Improve Oil Recovery - FNE Case Study, Sudan

Abstract

One of the main types of Enhanced Oil Recovery (EOR) methods is thermal stimulation method which is an increasingly common method of extracting heavy oil. there are different forms of the technology of thermal method Cyclic steam stimulation, Steam flooding and In-situ combustion “Fire flooding” are commonly applied to oil reservoirs, which are relatively shallow very viscous oil at the reservoir temperature, the most widely used steam injection methods for heavy oil recovery is Cyclic Steam Stimulation “steam soak or huff and puff” method.

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 the 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 recover factor from each well and each field.

In this paper the challenge facing Bentiu reservoir in Fula North East (FNE) located in heavy oil zone with target of production around 85% of the total reserves will be highlighted. The field has shallow depth ranging between 520m and 700m and low pressure gradient 1.09 psi/m, and with reservoir temperature around 44 ^oC.

The study covers an investigation on the benefits of steam adsorption to enhance the oil recovery focusing on the distribution of the steam inside the layers, also cover the analyzing and reviewing the actual steam intensity distribution among each layer in the two wells that are later compared with the designed ones. In a later stage, we designed a pilot model that 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 layers.

 An optimum steam injection protocol that will maximize the recovery factor from these oil zones has been designed and the results show that the injection rate has significant effect in steam distribution.

Keywords: Cyclic Steam Stimulation, Enhanced Oil Recovery (EOR), Steam-Assisted Gravity Drainage (SAGD), Hot water flooding and In situ combustion,