Fouling Mitigation for Laser Igniters in Natural Gas Engines

Due to several recent developments in lasers and optics, laser igniters can now be designed to be (i) compact so as to have the same footprint as a standard spark plug, (ii) have low power draw, usually less than 50 Watts, and (iii) have vibration and temperature resistance at levels typical of reciprocating engines. Primary advantages of these laser igniters remain (i) extension of lean or dilution limits for ignition of combustible mixtures, and (ii) improved ignition at higher pressures. Recently, tests performed in a 350 kW 6-cylinder stationary natural gas reciprocating engine retrofitted with these igniters showed an extension of the operational envelope to yield efficiency improvements of the order of 2.6% points while being compliant with the mandated emission regulations. Even though laser igniters offer promise, fouling of the final optical element that introduces the laser into the combustion chamber is of concern. After performing a thorough literature search, a test plan was devised to evaluate various fouling mitigation strategies. The final approach that was used is a combination of three strategies and helped sustain an optical transmissivity exceeding 98% even after 1500 hrs. of continuous engine operation at 2400 rpm. Based on the observed trend in transmissivity, it now appears that laser igniters can last up to 6000 hrs. of continuous engine operation in a stationary engine running at 1800 rpm.

Strategic Alliance Enables Fast-Track Engineering and Expeditious Deployment of Novel Flowable Sensors & Water Reactive Nano-Composite Plugs in MENA

Fast-track engineering to expeditiously deploy new technologies in upstream oil and gas heavily relies on timely agreement and synergy between the engineering team and stakeholders on (1) tool architecture (2) operational envelope and wellbore environment (3) qualification criteria(s) and overall verification & validation (V&V) strategy, among others which lead to the product specifications. Here we present a "Case Study" where two new technologies, were engineered to order for the Middle East and North Africa (MENA) regions: a first-generation Pressure-Temperature (P-T) flowable sensor from our "Teleo" product line, and a multilayered water reactive plug for multi-stage stimulation (MSS) and acid frac, designed from bulk ultrafine-grained light alloys and water reactive, nanocomposites.

Modelling and Performance Analysis of Stationary Gas Turbines Operating Under Rotational Speed Transients

In order to increase the flexibility and performance of gas turbines, generally their manufacturers and research centers involved in their development are constantly seeking the expansion of their operational envelope as well as their efficiency, making the engine more dynamic, less polluting and able to respond promptly to variations in load demands. An important aspect that should be considered when analyzing these prime movers is the assessment of its behavior under transients due to load changes, which can be accomplished through the development of a detailed, accurate and effective computational model. Considering this scenario, the present work aims to develop a model for the simulation and analysis of the dynamic behavior of stationary gas turbines. The engine considered in this analysis has a nominal capacity of 30.7 MW (ISO conditions) and is composed by a two-spool gas generator and a free power turbine. The model was developed using T-MATS, an integrated Simulink/Matlab toolbox, develop by NASA. The gas turbine was evaluated under both permanent and transient regimes and each one of its component was analyzed individually. The assessment made it possible to determine the engine performance parameters such as efficiency, heat rate and specific fuel consumption and its operational limits (surge limits, stall, turbine inlet temperatures, etc.) under different load conditions and regimes. The results obtained were compared with available field data, and the relative deviations for the considered parameters were all lower than 1%.

Towards approval of autonomous ship systems by their operational envelope

Current guidelines for approval of autonomous ship systems are focused on the ships’ concrete operations and their geographic area. This is a natural consequence of the link between geography and the navigational complexity, but moving the ship to a new area or changing owners may require a costly re-approval. The automotive industry has introduced the Operational Design Domain (ODD) that can be used as a basis for approval. However, the ODD does not include the human control responsibilities, while most autonomous ship systems are expected to be dependent on sharing control responsibilities between humans and automation. We propose the definition of an operational envelope for autonomous ship systems that include the sharing of responsibilities between human and automation, and that is general enough to allow approval of autonomous ship systems in all geographic areas and operations that falls within the envelope. We also show how the operational envelope can be defined using a system modelling language, such as the unified modelling language (UML).

Pushing the Operational Envelope of a Cap-Rock Restoration Campaign Utilizing Perforate Wash Cement Technology and a Hydraulic Work Over Unit Offshore Malaysia

Malaysia's government recognizes the high risk that aging idle wells pose to its health, safety and environment and has developed some of the most stringent plug and abandonment, P&A, regulations to protect its future. Corroded casing strings and sustained casing pressure are common issues on its multi-decade old platforms and a risk-based design philosophy has been adopted to balance risk mitigation and operational costs, while still ensuring an eternal barrier. Both conventional rigs as well as rigless hydraulic workover units, HWU, are being used for P&A operations. This study considers the barrier element rationale applied in four offshore wells that were plug and abandoned by cap-rock restoration Perforate, Wash, Cement, PWC, barrier plugs. It also considers the operating window of a jet-based PWC technology to understand the challenges and opportunities for further optimization during HWU operations. Cap rock restoration utilizing both cup-based and jet-based PWC technology is being widely applied throughout Malaysia as a cost-effective alternative to casing section milled barrier plugs. Malaysia's P&A regulation allows isolation at the cap rock level, whereby "Contractor shall adhere to the Cap-Rock Abandonment Applicability Flowchart to identify technically and commercially acceptable candidates for this well abandonment method." The PWC method enables cap rock restoration in a single trip process; whereby the casing annulus is accessed by TCP guns to allow for annular debris to be effectively washed prior to cement plug placement. The process is not limited only to TCP guns; as a mechanical casing perforator was utilized in a shallow cased hole section of one of the wells to avoid damaging the outer casing. A custom BHA was developed and tested to match the cuts from the mechanical perforator. Specially oriented, rotating, wash jets were configured to maximize the annular access during the washing process. The washing effectiveness of this new BHA was confirmed by the massive amount of annular debris that was observed over the surface shakers. Operations were conducted offshore with a HWU with limited infrastructure and operating capability compared to a conventional rig. A PWC candidate screening matrix was applied early during the planning phase to manage rig limitation, well condition and operational risk to ensure successful barrier placement. All cap rock barriers were successfully installed and tested, and no sustained annular pressure remained in any of the wells. Fewer PWC plugs were required than originally planned, due to strict adherence to the Caprock Restoration Plan Decision Tree, resulting in significant cost savings for the project. The detailed time breakdown of the HWU operations provides useful insight into the operational efficiencies and unplanned events during the HWU campaign and lessons learned are shared from the project.

Evaluation of a Full-Scale Suspended Sludge Deammonification Technology Coupled with an Hydrocyclone to Treat Thermal Hydrolysis Dewatering Liquors

Suspended sludge deammonification technologies are frequently applied for sidestream ammonia removal from dewatering liquors resulting from a thermal hydrolysis anaerobic digestion (THP/AD) process. This study aimed at optimizing the operation, evaluate the performance and stability of a full-scale suspended sludge continuous stirred tank reactor (S-CSTR) with a hydrocyclone for anaerobic ammonia oxidizing bacteria (AMX) biomass separation. The S-CSTR operated at a range of nitrogen loading rates of 0.08–0.39 kg N m−3 d−1 displaying nitrogen removal efficiencies of 75–89%. The hydrocyclone was responsible for retaining 56–83% of the AMX biomass and the washout of ammonia oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was two times greater than AMX. The solid retention time (SRT) impacted on NOB washout, that ranged from 0.02–0.07 d−1. Additionally, it was demonstrated that an SRT of 11–13 d was adequate to wash-out NOB. Microbiome analysis revealed a higher AMX abundance (Candidatus scalindua) in the reactor through the action of the hydrocyclone. Overall, this study established the optimal operational envelope for deammonification from THP/AD dewatering liquors and the role of the hydrocyclone towards maintaining AMX in the S-CSTR and hence obtain process stability.