Energy, Conventional and Advanced Exergy Analysis of Low Temperature Geothermal Binary-flashing Cycle Using Zeotropic Mixtures

Due to deep utilization of geobrine and high net power output, binary flashing cycle (BFC) is deemed to be the future geothermal energy power generation technology. The BFC using R245/R600a zeotropic mixtures is presented in this paper. The thermodynamic model of the system is built, and energy, conventional and advanced exergy analysis are carried out, to reveal the real optimization potential. It is demonstrated that the optimal composition mass fraction of R245fa and dryness of working fluid at the evaporator outlet ranges are 0.30~0.50 and 0.40~0.60, considering the thermodynamic performance and the flammability of the mixtures, simultaneously. Conventional exergy analysis indicates that the maximum exergy destruction occurs in condenser, followed by expander, evaporator, flashing tank, preheater, high-pressure pump and low-pressure pump. While the advanced exergy analysis reveals that the expander should be given the first priority for optimization, followed by condenser and evaporator. The BFC has a large potential for improvement due to higher avoidable exergy destruction, about 48.6% of the total system exergy destruction can be reduced. And the interconnections among system components are not very strong, owing to small exogenous exergy destructions. It also demonstrates the effectiveness of advanced exergy analysis, and the approach can be extended to other energy conversion systems to maximize the energy and exergy savings for sustainable development.

Holistic Customized Approach to Address Practical Challenges for the Large Scale Implementation of Limited Entry Liners Completions at ADNOC Onshore Fields

Limited entry liners (LEL) implementation strategy is one of the key solutions to to improve the well productivity by maximizing the reservoir contact and matrix stimulation carbonate reservoirs. This strategy requires conducting high rate and high volume acid stimulation with high pressure pump after the installation of limted entry liner, that poses practical concerns to be addressed for adopting conventional well completions and existing resources. In addition, implementation of the LEL completion and stimulation for a large scale application within the minimum time frame and limited resources is a challenge. This paper provides the detail of challenges faced and solutions adopted to implement the LEL completions amd stimulation at onshore fields. Challenges including suitable candidate selection, completion design, limited materials for well construction to handle high-volume acid stimulation, limited well head injection pressure, contractual limitations for securing the tools and pumping equipment. Further, this paper discusses about the temporary solutions adopted for executing the LEL implementation in the best economical way within near future and provide the long term solutions for LEL implementation in the next 5 years business. The first three LEL completion wells that were successfully installed and stimulated at ADNOC Onshore are currently producing at more than 2 times higher PI (productivity index) compared to the pre-stimulation rate. The same apply to the injector wells, in which significant improvement on the injection rate of up to 18bbl/min (26000 bwpd) was observed. Currently ADNOC Onshore is planning to execute the LEL completion and stimulation in additional 15 wells during 2021 along with plan for up to 300 LEL completions during the next 5 years. The LEL technology is a key technology to support ADNOC lower completion strategy which aim to minimize the bare foot completions in order to increase the horizontal wellbore accessibility and effective stimulation. Overall, the first LEL installation and stimulation completed within 8 months from the candidate finalization using the existing resources available in ADNOC Onshore. This paper describes an economical solution for implementation of LEL completion strategy at large scale for major fields within minimum time frame by utilizing the existing resources while adhering to HSE rules.

Pushing the Limits for Open Hole Zonal Isolation – Design and Qualification of Expandable Steel Packer

Enhancing gas productivity is linked to multistage stimulation (MSS). Choosing a cemented over uncemented solution is driven by factors such as operational efficiency, drilling practices, and isolation techniques. Swellable and mechanical packers have been used widely. A new packer type, an expandable steel packer, has been qualified recently, the expandable steel packer combines the strengths of mechanical and swellable packers and will provide an option for openhole completions. The 4.5-in. expandable steel packer design was optimized to meet most demanding applications with the following characteristics: reduced running outside diameter (OD) to 5.6 in., premium assembly technique by crimping, double sleeve pressure self-compensation, and use of nickel alloys for sour environment. After the design of the packer was completed, the 4.5-in. expandable steel packer was qualified according to the API Spec 19OH (API 2018) standard protocol at 15,000 psi with thermal variation between 320°F and 68°F. The packer was tested in a casing with inside diameter (ID) of 6.5 in. The test casing had an ID of 6.5 in. whereas nominal hole size ranges from 5.875 in. to 6.125 in. It was chosen to simulate a washout and considering the calculated maximum expansion ratio for the steel to verify the 15,000-psi pressure rating capability. The test casing was built with a heat exchanger, high-pressure pump, and pressure and temperature sensors. The packer was expanded inside the dummy well with all the measuring instruments in place. Expansion pressure signatures were observed as predicted. The analysis of the packer setting pressure curves showed expansion initiation and full casing ID contact. The liquid differential pressure test from each side of the packer proved the internal pressure compensation performed as expected. No leak was observed during the pressure steps of 15.000 psi held for 15 minutes while cycling the temperature from 320°F to 68°F and back to 320°F. The expandable steel packer utilizes a unique double-sleeve system for self-pressure compensation during ball-drop stimulation operations. The packer expandable sleeve is protected during deployment by the end fittings. Expandable steel packers exhibit robustness during running in hole, enable setting on demand, have a high expansion ratio, require no de-rating vs. hole size, and have low sensitivity to thermal variations.

Precise Cement Displacement with a New Cement Plug Tracking Method

During the primary well cementing operation, when the cement slurry is pumped into the annulus around the outside of the casing string, it is very critical not to over displace and let the displacement fluid enter the annulus. Traditionally, to determine when to stop the cement displacement operation, the top cement plug position is tracked volumetrically by dividing the displaced volume by the casing internal cross-sectional area. However, the volumetric method is prone to uncertainties related to displacement fluid compressibility, high-pressure pump inefficiency, flowmeter inaccuracy, and variance in casing joint diameters. The new cost-effective cement displacement monitoring method is based on the analysis of the pressure pulses generated by the top cement plug passing the casing. These pressure pulses are detected by the standard pressure transducer installed at the cementing head. When correlated with the casing tally, these pulses identify the plug position related to the completion elements that provide better accuracy than the volumetric method used conventionally. The case studies include the successful cement displacement monitoring example and the case where the plug was prematurely stopped 90 meters above the landing collar, which was revealed by the subsequent drilling and confirmed independently by the new plug tracking method.

Numerical-experimental optimization of the Common-Feeding injection system concept for application to light-duty commercial vehicles

The innovative Common Feeding (CF) fuel injection system has been designed for a light duty commercial vehicle diesel engine in order to reduce production costs and to allow easy installation on the engine, compared to a Common Rail (CR) system. In the CF apparatus, an additional delivery chamber is mechanically fixed at the high-pressure pump outlet, and the rail is removed from the hydraulic circuit. Experimental tests have been carried out on a hydraulic test rig in order to compare the general performance of the prototypal CF system with those of a CR system equipped with different rail volumes. In the cases of the double injections, the fluctuations of the injected mass pertaining to the second injections have been investigated during dwell time sweeps, and design solutions have been provided to minimize such oscillations. Moreover, an injection system numerical diagnostic model has been validated, and the reduced accumulation volumes linked phenomena have been analyzed. In general, the performance of the injection systems with different hydraulic capacitances or shapes of the accumulator are similar. One difference is that the injection rate features slightly different slopes during the rising phases; furthermore, cycle-to-cycle dispersions in the injected mass increase to some extent when the hydraulic capacitance is dramatically decreased. Finally, the frequencies of the free pressure waves, due to the water hammer occurring at the end of a hydraulic injection, are different when the shape of the accumulation volume changes, whereas these frequencies are independent of the accumulation volume sizes.

Analysis of changes in the angular velocity of the crankshaft of the marine engine for diagnosing the wear and location the failure of the fuel injection system

The combustion process can be simply described as periodic explosions in a cylinder with its frequency dependent on the number of cylinders and the rotational speed of the shaft. In practice, uniformity of combustion parameters in every cylinder is almost impossible. Due to this fact, instantaneous angular acceleration does not remain the same at the ends of the crankshaft. These observations formed the basis for the investigation of the instantaneous angular speed of the crankshaft ends. To investigate the influence of the failure behavior of the fuel systems during a shaft's rotational movement, a series of experiments were planned. For the simulations, a medium-speed marine engine driving electro generator was selected. The failure simulation was based on the installation of clogged spray holes, draining of part of fuel dose from high-pressure pump and decreasing of injection pressure by a lower tension of the injector spring. The results of measurement were processed and analyzed through a comparison of the fast Fourier transform spectra. As a general conclusion, a difference between general harmonics order of magnitudes was detected.