Abstract
Formation damage is an undesirable operational and economic problem that can occur throughout the lifecycle of oil and gas wells due to several reasons such as using incompatible fluids during workover operations, fines migration, clay swelling, emulsions formation, and scale and organic depositions. Also, newly drilled wells sometimes do not produce optimally due to the damages caused by the drilling fluids. Therefore, addressing formation damage issues to ensure optimum recovery of hydrocarbons needs more efforts on identifying the damage mechanism and quantifying the skin factor. Skin factor is a dimensionless number that reflects the production impairment due to near-wellbore reduction of permeability. So, if this number is zero it means the well is intact, however; if this number is positive that means the well is damaged. The workflow presented in this paper focuses on the use of fiber-optic telemetry-enabled coiled tubing (FOTECT) for production enhancement in real-time by quantifying skin factor, estimating the flow potential and determining the candidate wells for matrix stimulation. This new technology can deliver pressure data in real-time during a typical unloading operation that could be further used in well test analysis for estimating key reservoir properties such as skin (S), flow capacity (Kh), drainage area (A) and initial reservoir pressure (Pi). The new technology reduces the operational time required for well test analysis compared with conventional downhole recording systems (DHR) by two-fold while enabling the performance of an acid treatment in the same run. Moreover, in this study a workflow and user-interface software using java language were developed to execute the workflow through a two-step streamlined process: 1. Assessing the well damage through quantifying the skin value from pressure transient analysis (PTA) utilizing the downhole pressure data acquired from coiled tubing in real-time. 2. Inflow performance relationship (IPR) construction of the well using Vogel’s correlation and productivity index equation under the current condition and under ideal condition (Zero skin) to assess the feasibility of a stimulation treatment. The paper will present the application of this technique on simulated field data to show how FOTECT could be used to diagnose and treat the well in the same run. The output obtained from the developed software will be compared against the output of an industry popular well-test suite (Sapphire). Also, a case study in which this technology was used for pressure transient analysis for artificial lift design will be presented to show the applicability of this novel approach and to prove it can yield matching results with conventional techniques in a more efficient way. From the simulated data the developed software estimated the skin factor to be nine from both build-up and draw down analysis, which was later matched by Sapphire commercial Suite; moreover, it was shown that the current production rate of 792-BPOD can be increased to 1722-BOPD post a successful stimulation treatment.
Highlights
Nitters et al [1] indicated that 60 to 70% of matrix stimulation treatments fail worldwide due to a lack of structured approach in candidate selection and treatment design
A field application is discussed to prove the viability of this technology on performing pressure transient analysis and to show its advantages over conventional techniques (DHR on memory gauges)
Pressure data required for well test analysis was acquired by deploying memory gauges into the production tubing; some challenges were faced during well testing operations that encouraged the operator to try the fiber-optic telemetry enabled coiled tubing (FOETCT) for well testing [8]
Summary
Nitters et al [1] indicated that 60 to 70% of matrix stimulation treatments fail worldwide due to a lack of structured approach in candidate selection and treatment design. The motive for this study is to introduce and develop a new concept and workflow for performing candidate selection and well treatment simultaneously This workflow will leverage the capability of the new generation of coiled tubing units of downhole pressure data transmission via fiber-optic telemetry. In case it was concluded that formation damage is present as indicated by appositive skin factor, the same coiled tubing unit could be further used to treat the damage through a well-designed stimulation treatment in the same run saving logistical cost and time. The real-time pressure data obtained from the pressure sensor deployed with the coiled tubing is the key input required for pressure transient analysis. The well test engineer can adjust the test sequence by identifying wellbore storage period, infinite acting radial flow (IARF) and reaching the boundary Those benefits will save time and ensure accurate well test analysis [2]. The built model performs both tasks which are pressure transient analysis and inflow performance comparison and concludes if the well is a good candidate for matrix stimulation
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