A New Solution to an Old Problem: Tractored CT Conveyed Real-Time Water Injection Profiling in Ultra Deep Wells
Authors: Arukhe James , Al Ghamdi Saleh , Dhufairi Mubarak , Duthie Laurie , Yateem Karam , Almari Abdulrahman , Elsherif Tamer , Othman Bassem 
Published: May 2016

Intervention work is often necessary in field developments with deep wells to enhance well performance through acid stimulation. Acquisition of flow profile data in these wells is also vital for decision making. Deploying rigless solutions for monitoring of well enhancements and injection zones in the extended reach wells presents both technical and economic challenges given the tortuous nature of these wells, dogleg severity, considerable variations in azimuth and hole inclination, washouts and general hole conditions.

Significant intervention cost savings have been observed since hydraulic tractor-aided coiled tubing (CT) intervention was introduced in ultra deep wells in the development of a Saudi Arabian field three years ago. Specific stimulation benefits include reduction to skin damage, improved drawdown, and treatment gains from injectivity increase. While tractor aided coiled tubing has largely been demonstrated as a preferred deployment technique for cost-effective acid stimulation and memory production logging in extended reach wells, the subjects of real-time evaluation of treatment effectiveness and injection zone monitoring have remained an industry challenge.

The limitations of memory production logging have been compounded by spinner failure from organic residue dropouts in the wellbore while logging (which cannot be identified with the memory production logging tools until the end of the job). Apart from the lost time and loss of data, operational cost is extended beyond the allocated budget from re-runs, thereby adversely affecting development schedules. From this experience evolved a design to run real-time production logs in such challenging wells with potential for triggering data problems and delivering better quality wells. With improvements in job design, the first real-time production logging job trial was successfully performed in a 9.1 km well with a measured depth to the true vertical depth (MD/TVD) ratio greater than 3.44 in Saudi Arabia. This case study reveals how real-time information was employed to effectively stimulate and perform real-time production logs of an ultra deep well in Saudi Arabia. Practically, the work shows that effective stimulation and real-time production logging are possible in ultra deep wells.

Introduction

Through extended and mega reach technologies, the oil industry has been able to access reservoirs unattainable to conventional completion and drilling techniques. Blikra, Drevdal, and Aarrestad (1994) defined extended and mega-reach wells on the basis of measured depth to the true vertical depth (MD/TVD) ratio of the wells. According to the definitions offered by Blikra, Drevdal, and Aarrestad, wells with MD/TVD greater than 2.0 are extended reach wells, while the wells with MD/TVD ratio greater than 3.0 are mega-reach wells. For simplicity, extended and mega-reach wells are referred to simply as ultra deep wells in this discussion.

The purpose of the tractored CT enabled real-time production logging run was to enhance the gains of coiled tubing (CT) placement and the apparent mechanical diversion of stimulation fluid treatment across the entire + 6,697 ft open hole in an injector well. The reason for well stimulation was to reduce skin damage from mud filtrate and particle invasion from drilling and well completion fluids into the reservoir as well as to establish uniform contribution from the entire openhole horizontal section. Stimulating the injector wells will enhance their injectivities for a favorable waterflood during the injection scheme.