One of the advantages of having a dual string completion is the option to develop and produce more than one reservoir simultaneously, whereas there are considerable disadvantages too and one of such is managing the integrity of the two strings intact throughout the life time of the well. In this paper, a case study from Ahmadi Field is presented highlighting the need for effective surveillance methods to identify issues with dual string completion and successful implementation of workover.
Spectral Leak Detection (SPEC-LD) along with High Precision Temperature (HPT) tool was used to pin point the exact leak locations in the tubing strings prior to attempting the workover. Spectral Noise Tool is a passive tool with a high sensitivity hydrophone designed to record sound in the frequency range of 8 HZ to 60 KHZ. Analysis of noises recorded in various frequency ranges allows the location of flow-related features, such as wellbore flows, casing and tubing leaks, perforations, cement channelling and flows through the rock matrix and fractures. The SPEC-LD combined with a high-precision temperature (HPT) tool was found highly effective in pinpointing leak sources and quantifying it.
Ahmadi Field is one of the prolific oil fields in South Kuwait and has many dual string completions. In this paper, a case study is presented where the SPEC-LD tool was effectively deployed to identify leaks in a dual string completion. The leak and communication between the strings resulted in higher water cut from the short string which was producing at zero water cut. Based on the logging results, the well was successfully worked over in a cost-effective manner to improve the production. The workover also resulted in reducing the water production from the well, thus saving water treatment cost prior to disposal. Knowledge of the tubing condition prior to deploying the workover rig was found useful and effective in selecting the proper workover procedure, tools and techniques.
Blindly doing workover without knowing the tubing condition and well integrity generally results in the application of wrong workover processes and techniques causing overspending and safety concerns. Evaluating the condition of the tubing string and pinpointing the leaks was found useful in planning proper workover and thus minimizing the cost as well as bringing the wells back on line on minimum time. The main message from this paper is the benefit of using appropriate evaluation techniques prior to attempting any workover to save both time and money.