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Current acoustic (sonic and ultrasonic) techniques for cement evaluation have proved to be limited in providing unambiguous answers to the zonal isolation issue. This is especially true in lightweight cements where they often fail to differentiate cement from mud. Also, as far as imaging of the cement sheath is concerned, ultrasonic pulse-echo tools fail to image beyond the cemented region adjacent to the casing, thus providing limited diagnosis of the annulus. A new ultrasonic imaging tool has been developed to address these limitations. The new imager combines the classical pulse-echo technique with a new ultrasonic technique that provides temporally compact echoes arising from propagation along the casing and also reflections at the cement-formation interface. Processing these signals yields unprecedented characterization of the cased hole environment in terms of the nature and acoustic velocity of the material filling the annulus between casing and formation, the material immediately behind casing, the position of the casing within the hole, and the geometrical shape of the hole. Different wells cemented with conventional and light cements were logged with the new experimental tool. The results demonstrate enhanced cement evaluation for both cement types and significant reduction in the uncertainty in making a squeeze or no-squeeze decision. Introduction Cement evaluation logging tools have been used successfully for many years to evaluate casing and cement conditions. These tools, which use sonic or ultrasonic1 techniques, are designed for conventional steel casing and cements. The sonic tools, commonly known as Cement Bond Log or CBL, operate at frequencies of about 20 kHz and measure the amplitude or the attenuation of a wave traveling along the casing. The wave loses energy mainly though shear coupling to the surrounding cement, so that well-bonded solid cement attenuates more quickly than a fluid. Due to the low frequency, the CBL logs made with these tools lack azimuthal resolution, which makes it difficult to distinguish channeling from poor cement properties.

Logging hydrocarbon production potential of wells has been at the forefront of enhancing oil and gas exploration and maximize productivity from oil and gas reservoirs. A major challenge is accurate downhole fluid phases flow velocity measurements in production logging (PLT) due to the criticality of mechanical spinner-based sensor devices. Ultrasonic Doppler-based sensors are more robust and deployable either in wireline or logging while drilling (LWD) conditions; however, due to the different sensing physics, the measurement results may vary. Ultrasonic Doppler flow meters utilize the Doppler effect that is a change in frequency of the sound waves that are reflected on a moving target. A common example is the change in pitch when a vehicle sounding a horn approaches and recedes from an observer. The frequency shift is in direct proportion of the relative velocity of the fluid with respect to the emitter-receiver and allows to infer the speed of the flowing fluid. Doppler flow meters offer many advantages over mechanical spinners such as the ability to measure without requiring calibration passes, the absence of mechanical moving parts, the sensors robustness to shocks and hits, easy installation and minimal affection by changes in temperature, density and viscosity of the fluid thus capability to work even in highly contaminated conditions such as tar, asphaltene deposits on equipment. Despite being widely used in surface flow metering, ultrasonic Doppler sensor applications to downhole environment have been so far very limited. We present in this work an innovative deep learning framework to estimate spinner phase velocities from Doppler based sensor velocities. Tests of the framework on a benchmark data set displayed strong estimation results, in particular outlining the ability to utilize Doppler-based sensors for downhole phase velocity measurements and allows the comparison of the estimates with previously recorded spinner velocity measurements. This allows for the real-time automated interpretative framework implementation and flow velocity estimations either in conventional wireline production logging technologies and potentially also in LWD conditions, when the well is flowing in underbalanced conditions.

The objective of this paper is to depict the quantification of the production rates of the different phases in deviated wells with high gas-liquid relation using the Flow Array Sensing Tool (FAST). The readings of standard Production Logging Tools (fullbore flowmeter, density, and capacitance) are centralized, therefore they are affected if there is re-circulation of the heavy phase (liquid). The phase segregation and possible apparent down flow of the heavy phase makes it very difficult to determine the distribution of the produced fluids, and in some cases the spinner flowmeter tends to stop or gives inaccurate readings. The cause of these inaccurate readings is that the centralized spinner is affected by positive flow in the high side and negative flow in the low side of the wellbore, and the spinner shows no flow or even apparent downhole flow, when there is a real positive flow. The FAST tool used during the acquisition of the production logs is an ultracompact production logging tool (3 ft long) that is capable to measure multiphase flows with an array of 8 sensors, two in each arm and located 90° apart. These sensors are based on MEMS (Microelectromechanichal Systems), and among the interchangeable sensors we have optical probes that takes ultra-rapid measurements of the refractive index and can determine hold-up of water, oil and gas; the electrical probes that measures conductivity to differentiate hydrocarbons from water, and magnetic probes with micro-spinners to determine the flow rate. Both the three phase optical probes and the electrical probes have excellent response including water hold-ups over 90% that cannot be measured with a standard capacitance tool. The data logged with FAST in deviated wells was processed and interpreted to obtain the apparent flow velocity profiles of each of the 4 micro-spinners and with the three phase optical probes, and the relative bearing curves the velocity maps, and hold-up maps where obtained. The velocity map showed that there was negative flow in the low side of the well and positive flow in the high side while the hold-up map showed the light phase (gas) in the high side of the well. Both maps showed clearly the flow pattern and were used to quantify the production of each perforation and the total rate matched closely the surface rate (within 2% deviation). With the hold-up and velocity maps, the real flow rates were obtained with high confidence, and the flow pattern were shown clearly in deviated wells. The three phase optical probes, and electrical probes are excellent indicators of water and hydrocarbons inflow in a wide range of hold-ups.

Calliper logs provide valuable information on the shape and wear of casing and tubing strings at various times throughout their operational life. In turn, this information is used to determine the remaining design strength. To clearly distinguish deformation and wear from deviations due to manufacturing tolerance, the calliper measurements can be compared with a baseline log run soon after a tubular string has been run, or with surface inspection data. However, a baseline log may not always be available. This paper addresses these situations and provides an assessment of what useful information can be obtained.A mathematical model, based on the properties of the discrete Fourier transform is presented to determine the calliper offset centre and underlying tubular ovality from 6 or more equi-angularly spaced calliper readings. The series expansion approximation enables these parameters to be determined as a best fit from raw, un-centred data to a numerical accuracy of approximately 0.01% in a single pass. This is consistent with the accuracy and resolution of the currently available callipers. Complete numerical results from test cases based on exact geometric shapes, such as an offset circle and centred ellipse plus field examples are also included along with implementation notes. The same calculations can also be used to determine the underlying elliptic shape and orientation of an open hole calliper.In the casing specification API 5CT, internal dimensions are indirectly described in relation to the unloaded casing or tubing OD and wall thickness at surface conditions. The manufacturing tolerances and resulting uncertainties may be significant compared to the wear, but in some cases useful information can be obtained with corrections for downhole tension, temperature and pressure effects. Details of these corrections and a discussion of other sensitivities is also provided.Such algorithms are usually considered by the service provider to be proprietary and little quantitative material has been published on them or their interpretation. Also, data is often presented to the customer in only centre-corrected form, which greatly restricts future reprocessing. This emphasises the importance of acquiring and retaining the raw data.