Value of Cement Bond Logs for Evaluation and Improvement of Cementing Practices in Extended Reach Drilling ERD Wells

This paper discusses the value of cement logs as the core input to analyze the cement quality and validate the improvements made to cementing designs and practices of the intermediate casing string in Extended-Reach Drilling (ERD) wells. The ERD wells are being drilled from artificial islands in a field offshore in the UAE. The primary cementing objectives are isolating the reservoirs from their sublayers and protecting the casing against possible future corrosion across an upper formation. Cementing challenges include higher angle deviation, higher mud weight requirements resulting from an anisotropic, unstable shale formation present above the reservoir section. Effective reservoir management requires sound zonal isolation to eliminate crossflow between different reservoir units. In combination with standard cement bond logs (CBL), ultrasonic technology has provided detailed information about cement quality and a qualitative indication of casing position in the borehole. These have also led to valuable insight into how continued cementing designs and practices improved zonal isolation. Improvements in cement quality seen as a result of enhanced casing centralization, optimized hydraulic model, modified cement rheology, displacement rate impact, among others, were confirmed with the cement log evaluation program. The paper will present the ultrasonic and standard CBL responses, which support the enhancements made to the cementing design and practices that yield the desired results. The cement quality has been improved in the ERD wells intermediate section through strategic modification in cementing practices. Cement evaluation logs have played a significant role in validating the cementing methods’ development. Consistently improved zonal isolation results have opened up the opportunity for future efficiency gains by eliminating routine CBL.

REMOVAL OF HG(II) METAL IONS USING KAOLIN ADSORBENTS MODIFIED WITH ANIONIC SURFACTANT AND EFFICIENT ULTRASONIC ASSISTED

This study reported the reduction of metal Hg(II) from water using natural kaolinite (NK) based adsorbents compared with modified kaolinite adsorbents with Hexadecyl trimethyl ammonium bromide anionic surfactants using ultrasonic technology (SMK). These adsorbent samples were characterized using several different techniques such as FTIR, X-RD and AAS analysis. The adsorption capacity is influenced by variables such as the contact time and adsorben dosage. The results of the analysis reported that the maximum waste reduction efficiency occurs in modified kaolin (SMK), where adsorption occurs faster than natural kaolin (NK). The maximum persentation is 94.57% for metal removal efficiency using modified kaolin at the contact time of 45 minutes and the dose of adsobene 1.4 g, while kaolin without modification is 73.83% of efficiency at the contact time of 60 minutes the adsobent dose was 1.4 g. The use of the adsorption method with the help of ultrasonic technology is proven to be more efficient in accelerating the removal of Hg2+ ions by increasing the surface dispersion of the adsorbent with metal ions in water. The adsorption kinetics model that is suitable for calculating the adsorption capacity of the adsorbent in the removal of Hg2+ ions using unmodified kaolin is pseudo-second-order models.

Well Rehabilitation via the Ultrasonic Method and Evaluation of Its Effectiveness from the Pumping Test

The exploitation of groundwater reserves, especially for drinking purposes, is becoming increasingly important. This fact has created the need to maintain wells in the best possible functional condition. However, wells are subject to an ageing process during intensive use, which entails an increase in up-to-date resistances in the well itself and its immediate surroundings (the skin zone). This causes a decrease in the efficiency of the well (a decrease in the pumped quantity, a decrease in the specific yield, an increase of the drawdown in the well, and creation of the skin zone). The increased hydraulic gradient in the skin zone causes an increase in the inflow rate to the well, thereby inducing the movement of fine material towards the casing. This material can clog the well casing and injection ports, which is compounded by an increase in chemical and biological plugging of the skin zone. In cooperation with the company sonic technologies, GmbH. (Sailauf, Germany), an experimental ultrasonic technology-based well rehabilitation assembly was developed and successfully tested. This article describes the prototype development of the ultrasonic device, including its incorporation into the rehabilitation set and a demonstration of its pilot deployment in the MO-4 pumping well in Czech Republic with an evaluation of the rehabilitation effects using the authors’ software (Dtest_ULTRA). Based on visual inspection and the results of hydraulic and geophysical analysis, the high efficiency of the tested technology was demonstrated in virtually all monitored parameters, where an improvement in the range of 25–55% compared to the original condition was identified.

Case Study in Well Integrity Assurance with Enhanced Ultrasonic Technology for a Highly Attenuative Environment

While applying acoustics is not a new science, inherent uncertainties with these techniques are still not addressing challenges that limit confidence in well integrity programs. The Caspian region's significant challenges for cement evaluations include heavy mud and thick casing, as well as the high-pressure/high-temperature (HP/HT) nature of gas condensate wells, which reduces the contrast in acoustic impedance. Accordingly, difficulties have remained in the interpretation of conventional cement bond logs, which has led many operators to be suspicious of well integrity technologies. This paper focuses on the application of ultrasonic cement evaluation technology in the Caspian Sea, and compares results between advanced ultrasonic applications and traditional cement bond logs in heavy mud. The workflow is presented to integrate the advancement of this technology and to eliminate the uncertainties in well integrity analysis. Increasing confidence for further drilling of a high-pressure gas reservoir has been achieved by combining these various measurements that enable a definitive analysis of zonal isolation. The main objective of this well assurance program was to ensure zonal isolation and shoe integrity in order to drill ahead to perform formation integrity tests (FITs). However, obtaining high-resolution cement data in heavy, 2.16-sg, oil-based mud (OBM) was the biggest concern due to the limitations of standard ultrasonic technology. The wide disparity in acoustic impedance, combined with the low contrast between heavy mud and the cemented section, makes evaluation of cement quality and zonal isolation doubtful. Although well conditions challenged the standard measurements, the cement evaluation objective was achieved with the new technology by ensuring 360° azimuthal coverage in permeable sand zones capable of unwanted hydrocarbon production – i.e., preventing sustained casing pressure (SCP). Moreover, a strong and continuous 40-m cement bond prevented crossflow from charging zones through the wellbore and also acted as a barrier against corrosion. Enhancement of pulse-echo technology has proved that it can be applied in a highly attenuative environment to achieve high-fidelity data. Highly acoustic attenuative mud is a major challenge for acoustic ultrasonic technology to achieve a quality answer product for well integrity. To mitigate this problem, a new tool was developed with a highly sensitive low-noise transducer, and with special programmable (both voltage and frequency) firing circuitry, to enhance the transducer signal at the resonance frequency of the casing. The various features of the processing algorithm are also improved, based on the numerous laboratory and field measurements.

A Comparison Study of Several Ultrasonic Endoscopy Technology for Tubes’ Inspection

Ultrasonic technology has developed rapidly in decades. However, few ultrasonic technologies have been proposed for tubes’ internal inspection. In this paper, 6 types of ultrasonic endoscopic transducers are brought to detect volumetric and planar flaws in tubes. Steam generator tube is application target. Beam simulations are implemented and compared using an open source acoustic simulation toolbox to illustrate beneficial effects of the different transducers. The results show the proposed endoscopic array transducers can form focused ultrasonic beams in tube wall, which do helps when detecting complex defects, such as crevice with uncertain direction. A prototype circular array transducer with 64 elements is fabricated to demonstrate the design. A straight tube (Φ19 × 3mm) made of carbon-steel with 8 longitudinal grooves and 8 ring grooves of no more than 0.5mm width on both inner and outer tube wall are applied in endoscopy experiments. The results demonstrate the detection sensitivity of the circular array transducer reaches 0.2mm in both circumferential direction and axial direction. The combination of the above proposed transducers and advanced imaging algorithms such as total focusing method may build an integrated array ultrasonic endoscopic inspection scheme for the internal inspection of tubes.