Well clean-up is one of the most complex operations performed at the wellsite today. During clean-up, a well is flowing for the first time after initial completion or workover operations through temporary surface facilities to either conduct a welltest or to simply condition the well before connecting it to production facilities. Currently, there are no practical recommendations available that would summarize clean-up experiences and guide operating companies through the process of efficiently planning well clean-up operations. Conventional well clean-up operations are inherently challenging owing to the requirements for accurate data measurements, safe handling and disposal of produced fluids (hydrocarbons, completion brine, water, and solids). Experience has shown that it is nearly impossible to perform well clean up within pre-defined constraints and target criteria without an appropriate design, equipment selection and operations planning to account for the specificities of each situation. Steady-state flow simulators have been the standard tool to model pressure and temperature changes along the wellbore and through temporary production system during well clean-up process. Those assume either final stabilized conditions or a limited number of intermediate ones and formed the basis for equipment selection. But this approach has critical limitations in modelling flowing well behavior and fast-changing flowing conditions, and therefore in assessing operational flow assurance risks and the dynamic capability of the surface plant to handle produced fluids. The paper describes in detail today's challenges during well clean-up operations that combine the need for operational safety, minimal environmental footprint and flow assurance considerations that have to be balanced with costs and production performance optimization. The paper provides practical recommendations and presents multiple case studies highlighting the results and lessons learned from applying a novel, unique workflow based on the application of a transient-multiphase flow simulator. Combined with modern well-testing equipment such as modern test separators, remotely actuated adjustable chokes or environmentally friendly fluid disposal techniques, such advanced design allows performing clean-up operations efficiently while remaining within time, rates, pressure or emissions limits.

Well commissioning operations offshore encounter multiple organizational, operational and technical challenges that must be safely overcome to efficiently deliver high-quality service. Coiled tubing (CT) perforation and commissioning performed in hostile reservoir conditions and high pressure is one of the most complicated multiservice operations, especially in a sensitive aquifer ecosystem like the shallow Caspian basin. A comprehensive approach used to deploy an innovative solution to the challenges provided experience in such operations and lessons learned. An innovative perforation technique was selected for the project: electric-line-enabled CT for precise depth control in combination with an advanced gun deployment system for conveyance of long gun strings under pressure. New techniques were incorporated to improve equipment efficiency and reliability: detonation shock-resistant bottomhole assembly, two independent emergency disconnects, software to predict and evaluate shock load and dynamic underbalance, high-pressure H2S-rated and conventional connectors for a specialized tool deployment stack (TDS), rounded scallop guns, and high-tensile CT logging-head-disconnect weak points. To date, more than 10 well commissioning operations were successfully completed with this innovative method. Integrated service project management was a key approach to achieving successful results by effectively integrating multiple service lines. The technique proved to effectively minimize operational time, associated risks, improper equipment use, and interface failures between different service lines. The developed solution is a seamless integration of electric-line-enabled CT, the CT logging head, the gun deployment system for pressurized well conditions, and a set of wireline tools and specialized perforation equipment. The design was optimized to perforate the well in three or four runs at overbalanced condition (squeeze mode) in one rig-up job instead of the more than 20 wireline runs typical in conventional operations. Additionally, the use of CT provided the flexibility to perform pumping operations for well displacement, injection of an H2S scavenger, and stimulation, as per the operator's plan, without or with only partial rig-down. This was the first time that integrated service project with the described CT perforation technique was performed in the Caspian region. The acquired experience will facilitate design, preparation, and execution stages for such type of jobs with multiple services involved.

Well completion and commissioning operations offshore present a variety of technical and operational challenges in the quest to maximize well productivity and optimize the economic value together with focus on safety. This is very relevant to the perforation operations performed in hostile and high-pressure reservoir conditions encountered in a complex development project in the Caspian basin. We provide description of the project and the innovative solution applied, including challenges faced, experience gained, and lessons learned. To overcome challenges, we selected electric-line-enabled (e-line-enabled) coiled tubing (CT) for precise depth control, and the latest advanced gun deployment system for conveyance of long gun strings under pressure. Innovative solutions implemented throughout the project included the perforation-shock-resistant bottomhole assembly (BHA), two independent emergency disconnects, and tuned software to predict and evaluate shock load and dynamic underbalance. Some of the unique technical solutions were designed specifically for this project: high-pressure and H2S-rated connectors; specialized tool deployment stack; 15,000-psi working pressure 5.12-in. ID H2S-rated rounded scallop guns; shock-resistant electrical disconnect; and high-tensile CT logging head disconnect weak points. To date, more than 10 well commissioning operations were successfully completed with this innovative method—e-line-enabled CT perforation under high pressure. This perforation technique proved to effectively minimize operational time, associated risks, improper equipment use, and footprint on location. Such approach allowed safe and efficient perforation in a controlled well environment that resulted in accurate depth control and managed detonation shock load and overbalanced conditions, which avoided any well fluid influx or H2S release. The developed solution required seamless integration of innovative techniques and hardware, including e-line enabled CT, the CT logging head, the gun deployment system for pressurized well conditions, wireline tools and specialized perforation equipment. The design was optimized to perforate the well in three or four runs at overbalanced condition (squeeze mode) in a single rig-up job instead of more than 20 wireline runs. Additionally, the use of CT granted flexibility and increased operational safety to perform pumping operations for well displacement and well control, injection of H2S scavenger, and stimulation, as per Operator's plan, without or with only partial rig-down. This is the first time that the described CT perforation operation using such techniques has been performed in the Caspian region. The experience demonstrates a method to safely and efficiently facilitate perforation jobs under challenging conditions in the future.

This paper presents the first experience of using a system for transmitting downhole data to surface (a telemetry system) based on wireless acoustic signal transmission during drill-stem testing (DST) in four carbonate reservoirs penetrated by an exploration well on Dolginskoye field in the Pechora Sea. Because no fluid would be recovered at surface during well testing, the job sequence program was optimized so that a full set of geological data could be obtained for each carbonate reservoirs in one trip. The purpose of a wireless acoustic telemetry system is to provide a communication link between downhole and surface equipment by means of acoustic signals passing through the well testing bottom-hole assembly (BHA) and enabling a two-way communication channel to be established so that bottomhole data can be received on surface in real time, and downhole equipment can be monitored and controlled. The system allows operators to adjust the well testing program based on bottomhole pressure data and to check whether sufficient amount of data has been collected for the well testing objectives to be achieved. Using a wireless acoustic telemetry system during dynamic well testing has many advantages compared to conventional testing with no downhole telemetry: bottomhole data can be received during job execution, operators have opportunity to monitor and analyze testing data and rely on a full set of representative data received in real time to make decisions for optimizing the job sequence program. The paper emphasizes the significance of receiving average formation pressure data during DST operations as it clarifies geological framework of the intervals under investigation and makes it possible to compare them with pressure data obtained by wireline tools when testing reservoirs with low porosity and permeability. The paper demonstrates a testing procedure optimization process which resulted in saving time on one well up to 36 hours and on other two wells – up to 24 and 48 hours, respectively, where acid treatments were considered unnecessary. For the first time, dynamic well testing were completed on the Russian Arctic shelf in four carbonate reservoirs without any fluid recovery on surface, under an optimized testing program. Considering a short navigation season, this technology is ideal for real-time bottomhole data transmission applications.

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