Cased-Hole Saturation Tool is Crucial for Optimizing Production and Reducing Uncertainties in a Naturally Fracture Carbonated Reservoir, Offshore, Libya

Abstract Bouri Field is an offshore saturated oil-bearing structure. The reservoir is a fractured carbonated deposit, and during production, gas and water are moving into the oil zone at the top and bottom, respectively. Consequently, monitoring the contacts is essential to optimizing field production. Unfortunately, the Gas-Oil contact (GOC) remains an uncertain parameter which directly impacts the selection of the targeted zone. Since the gas is flared out and limited gas capacity is allowed in the surface facilities, therefore, reducing gas production is essential. In addition to gas production issue, many wells stopped producing because of high water cut. At the early stages of the production history, the reservoir pressure was high enough to enhance lifting the fluid naturally all the way to the surface. However, some wells struggle to flow naturally when the reservoir pressure gradually decreases. Even though, there are many reasons behind the high-water production, nevertheless, understanding the Oil-Water contact (OWC) will be extremely valuable in managing the undesired water. This paper presents work has been done to evaluate the current field contacts by performing cased hole saturation logging tool to optimize production and reactivate shut-in wells to a number of 17 wells in Bouri field. Well by well analysis was carried out to assess the field potential. The thorough evaluation included reviewing the wells events and operations, production and pressure history, fracture signatures, water production analysis. Considering set of criteria, a systematic approach was followed to select the key wells to be used for the saturation logging campaign to identify the regional contacts. These contacts will be an essential input to the workover program to mitigate the damage and control the unwanted water. As a result of the study, five wells were chosen for the saturation logging campaign. The campaign revealed a dramatic change in the contact. In some areas, the OWC has raised and covered considerable interval of the reservoir thickness. While in other areas, the gas has expanded and found its way to the perforation. By correlating the saturation profiles form the key wells, the oil zone was identified along the field and a perforation, water shut-off and stimulation campaigns were proposed accordingly. A acritical water cut was which above the wells cannot produce naturally was detected around 60% to 80% depends on the wells’ locations. Three wells considered for Electrical Submersible Pumps (ESP) to extend the wells life and maintain the production. It was recommended to perform borehole images to understand the fracture locations and density to be considered for any fracture network analysis. Building an accurate simulation model is another reason to update the saturation profile of such complex field.