The paper presents evaluation of passive ultrasonic logging tool deployed using E-line to assess casing integrity in 3 oil producing wells in South of Oman. In addition a comparison is offered between the ultrasound logging technology and a more conventional well integrity test using a hoist and multi-set plug that has been utilized to date. The ultrasonic log was run in a selection of oil producing wells, operated by beam pump. Those wells were confirmed as having well integrity issues from well surveillance data and were causing significant oil deferment (2.2% of total oil production). Those wells have a history of cementation challenges owning to heavy losses that occur within a water bearing zone located above the pay zone. This, combined with the presence of H2S and oxygenated water at this depth, has resulted in a number of corrosion related integrity issues across the field. The logging program was originally planned inside tubing with surface pressures of 1,800 psi but it was decided to log inside casing (without tubing) because leak was more severe than predicted (1 m3/min of leak rate). In wells A and B, leak points at 630 m and 225 m were identified and respectively verified. However, another leaking interval in well A was also identified from conventional WIT using hoist. In well C, no pressure held on surface causing lack of differential across leak which resulted in identification failure on first attempt (inside tubing). On second attempt (inside casing), unclear ultrasound reading was attained but seven leak points still can be identified after several log passes. The tool can save significant hoist time and will become viable alternative. In conclusion this paper illustrates examples of where the ultrasonic log has provided highly accurate leak detection, significant time saving and improvements in overall operating efficiency. The limits of the technology are also discussed with recommendations provided for the application of the service based on operational experience gained during the technical evaluation.

A plug and abandon (P&A) operation aims to isolate the subsurface from the surface and success is traditionally gauged by fulfilling arbitrary criteria such as a physical length of an annular barrier. Multiple examples exist where a perfectly legal barrier has leaked. This paper intends to demonstrate that a sufficiently sensitive noise tool can provide the closest measure possible to verification of "no leakage". The principle that fluid moving in a turbulent fashion will emit acoustic energy is very well established and is used in many successful noise logging tools. When the fluid movement is very small, the level of noise is correspondingly small, and conventional tools may miss them. A tool optimised for low energy sensitivity was evaluated in a series of text fixtures and cemented casing sections recovered from real wells to quantify the lower levels of noise detectability. Following this, logs were recorded in previously abandoned wells, detecting minute leakage despite full compliance with guidelines. An industry leading acoustic tool was redesigned from the sensor through to the electronics to enhance its detection range to as low as possible. The sensor to electronics design was optimised to lift the low energy response by a factor of 10, while the intrinsic baseline noise was lowered to significantly increase the dynamic range available. A field test confirmed the low energy response to be 25 decibel (dB) better than pre-modification. Controlled testing under a range of conditions for both liquid and gas leakage resulted in the detection threshold being delineated for a variety of conditions. In addition to this the examination of statistical sampling parameter revealed meaningful acoustic signatures associated with varying flow regimes at very low rates. Field validation of the tool in a previously abandoned well confirmed the low threshold of the optimised tool and an intermittent leak of extremely low rate successfully mapped. This paper demonstrates through controlled testing and field deployment that compliance with P&A barrier condition regulations absolutely does not guarantee zero leakage, but that an optimised acoustic tool is able to detect even very tiny leaks. The judicious use of such technology during the abandonment procedure to verify a barrier is actually sealing will prevent costly returns to remediate faulty procedures.

Downhole imaging technology has been widely utilized in recent years to help diagnose proppant distribution during hydraulic fracturing operations. Abrasion leading to entry hole enlargement provides strong evidence of proppant placement into individual perforations, and treatment volume can be inferred by measuring the magnitude of this erosion. Results from individual perforations are easily aggregated to cluster and stage level to provide information on overall treatment distribution. Two different technologies have been deployed for this purpose – an array of downhole video cameras able to capture a full 360 view of the borehole and, more recently, multi-transducer ultrasonic instruments. These services have been considered competitors, and arguments for and against both technologies have included their relative measurement resolutions and how this impacts result accuracy, along with sensitivity to ‘stick and slip’ effects on toolstring motion. Both technologies are also affected to differing degrees by the well fluid and the presence of diverters and proppant in perforations. The recent introduction of a toolstring able to simultaneously acquire images from both sensor types affords the opportunity to objectively compare results acquired under identical conditions and establish their merits and limitations. The paper considers the underlying physical principles of each of the measurements and reviews in detail the real world results from North American wells that have been logged using both technologies. The aim of the paper is to provide a more complete understanding of the technologies involved, and how they can be viewed as complementary rather than competitive when they are run simultaneously, allowing potential users to make fully informed decisions on when, why and how to deploy them. We will also demonstrate how the information derived from simultaneous application is of greater value than that derived from the individual technologies in isolation, and how this can be applied to further enhance completion design and frac execution for unconventional wells.

Depth is probably the most important measurement that can be made in the petroleum industry because it is the reference for all other measurements that may be recorded. The discrepancies between drillpipe depth and wireline depth are well documented and both suffer from limitations. The properties of carbon composite rod, including low stretch coefficient and negligible thermal expansion, when combined with advanced well entry modelling allow very precise determination of absolute depth. Carbon composite rod is an enabling technology for intervening in extended reach wells, and part of the qualification process has been the evolution and verification of the predictive simulation software, which has proven to be very accurate and reliable. Part of the output of the simulation model is the calculation of a tension/compression profile along the entire length of the rod with the BHA at any position along the wellbore, which allows the extremely accurate calculation of the total cumulative stretch at any point along the wellbore, and hence the absolute position of any measurement devices. Carbon composite rod does not behave like drillpipe, wireline or coiled tubing so traditional modelling software cannot be used to simulate well entry. A bespoke mathematical technique was developed to fully describe the behaviour of the rod in a downhole environment and was initially used to predict well entry parameters, assisting in planning. Following each intervention, predictions were compared with actual performance for both surface weight and downhole cable head tension. The software's facility to assign individual friction factors to the rod and individual BHA components, and also to any area of the completion, was used to build extremely detailed well models in order to overlay calculated and measured parameters. With the model built, cumulative stretch with the measurement BHA at any point can be calculated with great accuracy. The results showed that the trajectory of the well bore and any areas of isolated high friction can have a very large effect on stretch and can render traditional stretch corrections liable to extreme errors. Further modelling in a variety of different well trajectories was undertaken to build further understanding of localised stretch effects and showed that even in complex wells stretch may be described by fourth order relationships with depth. The paper will demonstrate that the physical properties of carbon composite rods allow very precise modelling of cumulative stretch along the entire wellbore even in complex trajectories. This raises the prospect of being able to record a reference log of absolute depth which can then be used correct any previous data. Should the reference log be a continuous gyro survey, the absolute position of the well bore in 3 dimensions may be derived.

The ability to intervene in extreme extended reach wells using conventional technology has lagged behind the ability to drill and complete them. This paper intends to describe how the physical properties inherent in carbon composite materials provide a means of deploying logging tools into such a well in combination with a high-performance tractor, and to document a case study where a total depth of 40,600 feet (ft) was achieved against a production flow of 6,500 barrels of oil per day (BOPD). Extending the distance that a toolstring may be conveyed into a horizontal well by means of tractoring devices is well established. The medium for the conveyance becomes the critical component of the system to both maximise the ultimate depth achievable and to ensure safe retrieval. Low friction, low weight and high strength of the rod all combine to reduce required tractor loading and ensure safe recovery. The rod rigidity confers exceptional depth accuracy and removes the potential of tool-lift at high production rates, allowing logging under conditions that are truly representative of commercial well operation. A well that was drilled to a depth in excess of 40,000ft measured depth, with a trajectory designed to maximise the contact between wellbore and reservoir, was completed with a limited entry liner. A total of 37 compartments with lengths between 700ft and 900ft were separated with swell packer assemblies along a horizontal section of 25,000ft. Critical information about the production flow, including toe/heel balance, had been unavailable because of the limitations imposed by the available intervention methods. The intervention was designed to fully exploit the physical properties of the carbon composite rod in combination with the most efficient in-well controlled tractoring technology available, and aimed to reach deeper than 40,000ft. Simulations based on previous experience showed that this depth would be achievable with the tractor chosen and further that this could be achieved even with the well flowing at rates of over 5,000BOPD. This meant that deferred production could be minimised along with waiting periods for flow stabilisation. The intervention was successfully concluded in a single operation, gathering production data from as deep as 40,600ft. Performance of both rod and tractor aligned with planning simulations with significant margin, indicating further performance enhancements in reach being readily achievable. Drilling of such extended reach wells from existing islands will reduce well counts, accelerate development and increase oil recovery by unlocking reserves from the tight rock and areas that are currently unreachable from existing islands and wellhead platforms. Technology solutions like carbon composite rod and high-performance tractors enable the operators to acquire production logs & perform well services effectively to maintain the life cycle of extended reach wells inaccessible with conventional solutions.