A deviated newly drilled gas well in Western Caspian Sea in Azerbaijan, with a flowing water reservoir pressure of 17,500-psi and a flowing gas reservoir pressure of 12,200-psi was unable to regain flow after an unsuccessful attempt to bullhead produced water back into the well. During the bullheading operation, there was a peak registered pumping pressure of 12,933-psi without admission of fluid into formation. Producing interval was 5880mTVD with a MASP of 9,700-psi for gas reservoir. Coiled Tubing was the most viable option to identify the problem, to solve it and to regain access to the lower completion and then proceed with interval abandonment program. This being an unconventional well in multiple aspects, presented serious challenges accentuated in Safety, Well Integrity Control, Obstruction Removal, and Well Conditioning Plan Forward. Integrity of completion was believed to be compromised by the high pumping pressures applied during bullheading and a confirmed communication between production tubing and "A annulus". After performing 2 rig site visits, an action plan was issued to adjust the platform for a Coiled Tubing intervention for the first time. Points to be developed in the plan were HSE, Structural Analysis and modifications required for proper equipment accommodation. For well integrity control, it was imperative to evaluate the potential scenarios which could have led to the problematic well status. Completion history and specifications were reviewed to assure each of the potential operating scenarios could be controlled without compromising well integrity. On obstruction removal, simulation software was used to design procedure with optimum string, chemicals, rates and fluids to be used for the operation and which contingency fluids considered to be available offshore. It is challenging to perform effective cleanouts in completions with 2 different sizes of tubings (IDs 3.74" & 2.2") combined with restrictions (1.92" nipple), the success is a function of overcoming limited fluid pumping rates, slow annular velocities, particle sizes, cleaning speeds, among others. Well conditioning for future completion operations was planned depending on successful achievements of the coiled tubing intervention. A total of 14 runs with coiled tubing using different BHA configurations were performed to complete the scope. Well was safely and successfully cleaned from a starting depth of 2,512mMD to a target depth of 5,864mMD (5,610mTVD) by removing mud deposits, consolidated sand bridges and completion restrictions. Throughout the cleanout operation, best practices discussed on planning stage were applied to remove multiple obstructions encountered and dealing with potential corkscrewed casing. By accomplishing the well delivery, it is evident that the methodology followed during the planning stage and execution, was crucial to save the well from being lost or abandoned. There was an uncertainty whether the completion integrity was compromised by the high pressures used during the bullheading operation. Novelty in this intervention was the methodology for the risk assessment for an unconventional live well intervention with a 17,500-psi BHP, unseen pressure in the region. Thorough structural analysis was performed to assure the coiled tubing equipment could be placed safely on the platform to condition the well to regain production

Index of sand production is one of the major issues faced in oil and gas wells on the Caspian region. Although there are multiple technologies to address this issue, the application of these technologies require the well to be cleaned before proceeding with any kind of remedial application. Concentric Coiled Tubing (CCT) sand vacuuming technology has brought a massive advantage for efficiently cleaning the wellbore of sub-hydrostatic wells in Caspian Sea. CCT system is the Coiled tubing string inside of Coiled tubing string which essentially provides a smaller second annular return route for the wellbore solids while simultaneously boosting the return pressure and allowing us to clean the sand where the bottomhole pressure (BHP) is low and not enough to support the circulation of fluids used for the cleanout. Cleanout fluid is pumped through the inner string to power the downhole jet pump comprised in CCT bottomhole assembly (BHA) which creates a drawdown that vacuums the solids and circulates the solids back to surface via the CCT annulus. The solid performance of the CCT system has an established track record worldwide and application of this sand cleanout technology brought a solution for recovering many wells with low BHP and has been successfully implemented since 2013, providing a method for cleaning out tons of accumulated sand particles from challenging wells in Caspian Region. With the complex system being used for cleaning out sand and also surface handling of the solids in the return flow from the wellbore, CCT sand vacuuming technology has proven to be effectively functioning in all cases that it was selected for so far. This Paper reviews the design and mechanism of the CCT sand/well vacuuming system as well as the results of several well intervention cases with its successful execution and lessons learned in Caspian region.

Авторское право 2015 г., Общество инженеров нефтегазовой промышленности Этот доклад был подготовлен для презентации на Каспийской Технической конференции и выставке SPE, 4 -6 ноября, 2015, Баку, Азербайджан.Данный доклад был выбран для проведения презентации Программным комитетом SPE по результатам экспертизы информации, содержащейся в представленном авторами реферате. Экспертиза содержания доклада Обществом инженеров нефтегазовой промышленности не выполнялась, и внесение исправлений и изменений является обязанностью авторов. Материал в том виде, в котором он представлен, не обязательно отражает точку зрения SPE, его должностных лиц или участников. Электронное копирование, распространение или хранение любой части данного доклада без предварительного письменного согласия SPE запрещается. Разрешение на воспроизведение в печатном виде распространяется только на реферат объемом не более 300 слов; при этом копировать иллюстрации не разрешается. Реферат должен содержать явно выраженную ссылку на авторское право SPE.

A deviated well in Caspian Sea with 5-in open hole gravel pack (OHGP) screens started production on 2009 (Fig. 1). Oil production rate was stable until mid-2017 when it started to decline rapidly with a water breakthrough that reached 90% before well was shut-in on early 2022. Due to wax deposition in the tubing, 30 m3 of wax dissolver was injected in mid-2022, before the well was shut in. A de-completion operation to isolate existing reservoir and sidetrack started on mid-2022. During a slickline operation with a 4.275-in. drift, a hold up depth was reached at 60m MD recovering heavy wax on tool string. With a 3.5-in. gauge cutter and 3-in. dump bailer, maximum depth reached was 145m MD. At this time, a decision was made to perform a Coiled Tubing (CT) clean out operation until target depth of 4,200m MD for de-completion operation. Three runs were performed with a tubing encapsulated electrical wire enabled CT telemetry (CTT) system which consists of a customized Bottom-Hole Assembly (BHA) that transmits real-time differential pressure, temperature, and casing collar locator (CCL) data for depth correlation to surface through a non-intrusive tube wire installed inside the CT. For the first time in the region, a Tension Compression Torque (TCT) sensor was deployed with a High-Pressure Rotary Jetting (HPRJ) tool to control the wax clean out process with accurate measurement of axial forces downhole. After successfully reaching 215m MD with HPRJ tool, two additional runs were done with the CTT system. First, a drift run with 5-in Outside Diameter (OD) fluted centralizer to confirm 7-in tubing section clearance up to 199.3m MD and a second drift run with 4.275-in fluted centralizer to target depth at 4,200m MD to confirm 5.5-in tubing clearance. Figure 1Well 3D Survey CTT technology was a key element to successfully clean out wax on the 7-in and 5.5-in tubing sections. De-completion operations were completed after this intervention as follows: set a bridge plug at 4,115m MD, cut the 5.5-in tubing at 4,084.5m MD, circulate the well and pull out the upper completion to prepare the well for subsequent sidetrack operations. Using the CTT system and TCT sensor for real-time data monitoring of the HPRJ tool at bottom-hole conditions during a wax clean out operation was proven, thus, expanding their use in the field.

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