Horizontal Water Shut-Off for Better Production Optimization and Reservoir Sweep Efficiency (Case Study)

Abstract

Abstract Water production is a major problem for any oil and gas field. If not properly managed, unwanted water production will seriously impact the economics of a project through lost hydrocarbon production, reserves recovery and ever increasing treatment costs. It may cause major economic and operational problems for several reasons. It requires increased capacity of water separation and handling facilities, decreases hydrocarbon production, and results in large amounts of produced water that need to be disposed in an environmentally friendly manner. Some fields in Saudi Arabia use water injection for reservoir pressure maintenance, which makes water production and handling a necessity even at a relatively early stage of some of these fields life cycle. As drilling technology advanced in the past years, horizontal wells became the norm in many fields managed by Saudi Aramco, especially in the giant Ghawar filed, the largest oil filed in the world. Some of these wells started cutting water, and as the water cut increased the need to perform rigless water shutoff was needed due to the high demand and high cost of workover rigs. This paper will highlight the methodology, equipment and procedure used in the first rigless horizontal WSO in South Ghawar area by Coiled Tubing (CT) intervention to isolate the water producing zone at the toe of the well with a through tubing inflatable packer and a cement cap topped with mud push and high viscosity gel to reduce the cement slumping effect. Introduction Some horizontal wells started to produce less oil rate due to increasing water production. Basic horizontal well completion in South Ghawar was 4 ½ - 3 ½ tubing of an existing vertical wellbore and 6 1/8 inches open hole completions. Production flow profile is needed to determine the water producing intervals and come up with the best method to isolate that section. The production profile indicated that water production is from the toe of the horizontal open hole section. Job Objective and Design The objective of the operation is to shut off the water production zone by plugging back the lower zone. Production engineering evaluated all the available techniques to conduct this job with out utilizing a workover rig and was able to do so as this paper will show. The best available option was found to be setting an inflatable packer at the top of water zone in the open hole and cap it with 200 ft of cement and 300 ft of gel plug. The cement in conjunction with gel plug must be carefully designed to reduce the chance of cement slumping. Coiled Tubing Forces were simulated in order to determine if CT can get to the target depth without locking-up, and that the maximum tensile and compressive loads required at the packer during the operation are within the string capabilities and limitations. The friction coefficients were estimated based on the available friction data in offset wells.