The paper describes the execution of a successful rigless intervention solution deployed to establish well integrity and restore well production in a field in Europe. The paper will go through the planning and execution of the job highlighting the criticalities encountered and the overall benefit of the activity. The approach used was a deep analysis of the well integrity issue from several prospectives. A new opportunity in the production optimization fluid has been identified. After an open discussion between Customer and contractor, a customized blend and detailed pumping procedure was agreed upon to reach the final scope. An injectivity test was executed to align the procedure to the reservoir and well behavior. Several pressure tests were performed to confirm the remedial job in place, and, after that, the well was re-perforated and opened to the production. The horizontal well described in the paper, shut in during 2016 due to formation damage and depletion was selected for a new through tubing perforations interval by coiled tubing in the horizontal section. An unexpected firing head activation occurred at an unplanned depth, just above production packer. This event produced communication across the production tubing, liner, casing, and formation, which immediately induced total losses into the naturally fractured carbonate reservoir causing well control issues. The accidental perforations could have jeopardized the final scope of the project with no oil production and premature well abandonment. A successful rigless remedial intervention was immediately executed to restore well integrity by using a real time fiber optic coiled tubing acquisition and a new conformance fluid combined with a customized cement packer technique. The remedial intervention allowed the operator to resume the initial project's scope of opening the new perforation intervals, restoring an important oil production of about 150 [m3/d]. The final solution utilized a product with unique thixotropic properties which was then engineered for production optimization using a detailed pumping strategy. This novel approach added significant value, as the operator was able to restore the integrity of the well in rigless mode, avoiding the associated rig cost.
Usually, the preferred way to restore production in wells with accessibility heavily compromised is by rig workover activity. However, a preliminary approach in rigless mode followed by rig activity can be even more effective in the presence of several critical issues. Here we illustrate the methodology and technical solutions adopted to perform a challenging rigless fishing job to make the subsequent rig workover operation quicker, cheaper, and safer. A workflow was developed for a course of actions to perform a complex fishing intervention while fully respecting the well control requirements. Considering the well status—1½-in. coiled tubing (CT) stuck in 4½-in. tubing at 7582 ft due to scale buildup, parted in two segments side by side, top of fish at 1345 ft and with no injectivity in the well—it was decided to adopt a fit-for-purpose rigless strategy by combining conventional fishing tools (flow release overshot, continuous cutting overshot) with a CT anchor, which guided the electrical line (EL) cutting tools inside the pipe while keeping it in tension. To accomplish the target, a robust design, with multiple contingency plans was properly defined and successfully implemented. In addition to the main constraint of having a CT pipe parted and stuck in the tubing, the scale deposit prohibited killing the well by bullheading. Consequently, the overall fishing operations were planned and managed as if the well was alive. The alternate use of CT fishing tools, CT anchor, and EL cutting operations allowed recovering approximately 6958 ft over a total length of 7398 ft, leaving just 440 ft of CT pipe stuck in hole inside the scale deposit (with the new top of fish at 7142 ft). As a result, a complex well situation, which could have led to a long and expensive rig operation, was successfully approached in rigless mode, leaving the well ready for a simpler workover activity. The use of Continuous Cutting Overshot (CCO), through a standard "cut & drop" approach, was limited by the CT lubricator height. An innovative fishing approach was then deployed: a proper CT anchor BHA, to latch and hang the CT pipe in the tubing wall, was run. The beveled shape of the CT anchor allowed EL tools to enter inside the CT pipe and cut the same above the free point, so recovering longer sections of pipe.
Historically, the preferred method for restoring production on oil producers in a mature field in South Europe (Field A) was bullheading a matrix acid stimulation treatment. Even if successfully implemented, bullheading treatments at matrix rate are not always optimum and, for Well A, it was decided to diagnose the producing interval first to deliver a better selective stimulation treatment through coiled tubing (CT). This paper presents a novel approach implemented and discusses its associated benefits. Real-time (RT) fiber-optic (FO) CT (RTFOCT) technology was selected to diagnose this well for such benefits. These include accessibility of the producing zone (horizontal section), pumping capabilities, and versatility in executing different well interventions using single equipment. The technology is composed of a FO cable preinstalled into the CT pipe and a modular sensing bottomhole assembly (BHA). In addition to be the telemetry medium for the sensing BHA, the FO can be used as a sensor for distributed temperature and acoustic sensing (DTS and DAS). Having access to downhole information in RT helped to implement the decision-making process more quickly. DTS and DAS were used to evaluate the reservoir performance before perforating and assessing well performance, post perforation and stimulation. The sensing BHA helped ensure accurate placement of the perforations and stimulation treatment using a RT casing collar locator (CCL) and gamma ray (GR). Monitoring the bottomhole tension and compression allowed the operation to be performed in a safer and more reliable environment. RTFOCT allows interval diagnostics, stimulation treatment, and evaluation in a single CT run. Having the RTFOCT available also allows quick reaction to unexpected well problems, making diagnosis and remediation easier and faster. Moreover, one of the main goals for well monitoring and field management consists of production optimization activities designed to decrease Water Cut (WC). This has been made possible thanks to the detailed downhole dynamic characterization of the specific water flooding zones coming from RTFOCT, which allows Operator to stimulate the matrix in the right zone to enhance well performance, as well as design focused Water Shut-Off (WSO) interventions. The focus of the paper lies in the capabilities of the Operators to effectively manage this new tool in order to perform downhole analyses in real-time. This enables potentially problematic or complex scenarios to be identified early on, allowing time to react before they fully develop, thus increasing the percentage of success of the planned job, as experienced in the case study presented.
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