Water Field Distribution Characteristics under Slope Runoff and Seepage Coupled Effect Based on the Finite Element Method

The unsaturated seepage field coupled with heavy rainfall-induced surface flow mainly accounts for the slope instability. If the slope contains macropores, the coupled model and solution process significantly differ from the traditional one (without macropores). Most of the studies on the variation of the water field under the coupled effect of runoff and seepage on the slope did not consider the macropore structure. In this paper, two coupled Richards equations were used to describe the MF (Macropore Flow), and along with the kinematic wave equation, they were applied to establish a coupled model of SR (Slope Runoff) and MF. The numerical solving of the coupled model was realized by the COMSOL PDE finite element method, and an innovative laboratory test was conducted to verify the numerical results. The effects of different factors (i.e., rainfall intensity, rainfall duration, saturated conductivity, and slope roughness coefficient) on water content and ponding depth with and without macropores were compared and analyzed. The results show that infiltration is more likely to happen in MF than UF (Unsaturated Flow, without macropore). The depths of the saturation zone and the wetting front of MF are obviously greater than those of UF. When SR occurs, rainfall duration has the most significant influence on infiltration. When macropores are considered, the ponding depth is smaller at the beginning of rainfall, while the effects are not obvious in the later period. Rain intensity and roughness coefficient have significant influences on the ponding depth. Therefore, macropores should not be ignored in the analysis of the slope seepage field.

Detection of Leishmania donovani in Wild-Caught Phlebotomine Sand Flies in Endemic Focus of Leishmaniasis in Himachal Pradesh, India

An endemic focus of cutaneous leishmaniasis (CL) is located in the Sutlej River Valley in Himachal Pradesh (India) in the north-western Himalaya where CL co-exists with visceral leishmaniasis (VL). In areas of the Indian subcontinent such as Rajasthan, cutaneous leishmaniasis is transmitted by Phlebotomus papatasi (Scopoli) and Phlebotomus salehi. In Himachal Pradesh, Phlebotomus longiductus (Parrot) is suspected to be the vector for CL. In the current study, sand flies were collected and tested for Leishmania infection and to confirm the vector species causing CL. Sand flies were collected during April and September of 2017–2019 from CL endemic villages of Rampur (Shimla), Nirmand (Kullu) and Nichar (Kinnaur) districts of Himachal Pradesh. The sand flies were identified as Phlebotomus (adlerius) longiductus (Parrot) and Phlebotomus (larrousisus) major (Annandale). The density of P. longiductus was found highest. The elevation of villages ranged from 947 m to 2,130 m and were far from the presence of subsoil water. Field collected sand flies tested positive (7.69%) for Leishmania donovani by PCR-RFLP. The L. donovani sequences detected from P. longiductus were 97% similar to L. donovani sequences reported from the cases of CL in Himachal Pradesh.The Leishmania positive sand flies were morphologically identified as Phlebotomus adlerious longiductus providing one step further evidence towards the vector status of CL in Himachal Pradesh. The findings of the study are of epidemiological significance for strategic planning of vector control for leishmaniasis in India.

The Deep Water Field Alpha Plug and Abandonment Campaign – An Integrated Approach to Optimize Operations and Costs

After having been developed in the early 2000's and put on production since then, the deep water (700 M water depth) Field Alpha is now at the end of field life and in the plug and abandonment (P&A) process. Although this field-life phase does not make any money for an E&P operating company, it can be a liability and put the company's reputation at stake, if not done correctly. Therefore, like any other field-life phases, it requires a professional and multidisciplinary integrated approach to deliver it while reducing the company's exposure. P&A campaign involves many stake holders: the local authorities, its technical and operational representative / auditor, the operator's well engineering community, the subsurface team, e.g., petrophysics team, and the operator's management. Understanding all their expectations and KPIs is primordial to prepare and successfully deliver such operations. The P&A process relies on the placement of adequate "barriers" inside the well to guarantee blockade of any potential reservoir fluid communication either within separate reservoirs (to avoid any reservoir re-pressurization through cross flow) or with seabed / surface which could impact the environment. As part of the well barrier, annuli cement quality and efficiency must be checked by cement bond evaluation. The petrophysics team has the responsibility to both define, in collaboration with others team members, the cement quality criteria and then to evaluate the cement quality in timely and efficient manner. In this campaign, which is expected to run for more than a year, with several petrophysicists involved both in the preparation phase and in the operation phase, e.g., execution and results validation, consistency in the process is of utmost importance. This paper presents the workflow put in place by PETRONAS Carigali during the Field Alpha P&A campaign. It emphasizes on the petrophysicist role and responsibilities from the preparation phase, during the operations, and through the results validation. The learnings and experiences acquired during the Deep-Water Field Alpha P&A campaign are now going to be transpose to domestic and international assets by means of corporate guidelines and workflows.

Field experiment on flow stabilization of working fluid in a top-heat-type thermosyphon

To address the problem of global warming, increasing efforts are being made to use renewable sources of energy, such as solar energy, wind energy, and geothermal energy. However, the effective use remains a major challenge for its sustainable development. In this study, we used a top-heat-type thermosyphon to heat water using solar energy and transport the low-density hot water from the source to the sink (high to low elevation) without an external power source. The transported hot water can be used for cooking, bathing, underfloor heating, and heating homes and buildings, and warming cold springs. However, a disadvantage of top-heat-type thermosyphon is the intermittent flow of the circulating working fluid under low solar radiation. To address this issue, the authors proposed and developed a control system to stabilize the intermittent flow and prevent equipment damage and failure due to the sudden boiling of water. Field experiments were conducted to assess the practicability of the developed controller. The results showed that the controller efficiently converted the intermittent flow of working fluid to continuous flow by reducing the pressure in the buffer chamber and thus lowering the boiling point of the working fluid in the header of the solar collector.

SEISMIC RESONANCE: WAVELET-FREE REFLECTIVITY RETRIEVAL VIA MODIFIED CEPSTRAL DECOMPOSITION

Spectral decomposition is a proven tool in seismic interpretation, aiding interpreters to highlight channels, map temporal bed thickness and other geological discontinuities. Once seismic data is spectrally decomposed, notch patterns in the amplitude spectra are indicative of the reservoir layer’s thickness and/or its interval velocity. Additional cepstral decomposition will allow direct extraction of bed time-thickness or arrival time under particular reflectivity series setup. We build on these observations to establish a more generalized workflow for reflectivity retrieval method without the need to understand the details of the wavelet, provided the starting seismic is stably phased via phase correction during processing. We demonstrate reflector time and its ‘apparent strength’ can be identified in a transformed seismic resonance domain resulted from a modified cepstrum analysis. In this domain, each reflector can be characterized from obvious linear hot spots. The timing and strength of those linear hot spots will reveal reflector times and scaled reflectivity coefficients. This new method is subsequently applied for thickness prediction of a target reservoir in a complex geological setting, with large thickness variations and weak impedance contrast with underlying lithology previously complicating identification of base-reservoir. In a deep-water field blind test, the sand thicknesses evaluated from this method are found to be close to true vertical thickness found in wells.

Reservoir Souring Prediction in Deepwater Reservoirs for Field Development Planning

A deep-water Field X with two major Reservoirs U and L discovered recently offshore Malaysia is on development for early production. The subsurface plan for the Field X includes water injection. But the presence of sulphate rich seawater can provide a favorable environment for souring activity to take place. This study evaluates the reservoir souring potential for the green Field X as a result of seawater flooding. Reservoir souring is the increase of the hydrogen sulfide (H2S) concentration in produced reservoir fluids. As hydrogen sulfide is a highly toxic and corrosive gas, the production of H2S has a huge impact on the safety, infrastructure and facilities of the field. Whether a reservoir is susceptible to souring is dependent on a variety of factors. Some of these include water injection flow rate, temperature of the reservoir, presence of bacterial nutrients and rock minerology. Effective prediction of biogenic reservoir souring using computer models is essential when undertaking major technical and economic decisions regarding field development. For H2S concentration calculation PETRONAS utilized in-house stand-alone modeling tool that considers physicochemical hydrodynamics of multiphase flow, heat transfer, substrate propagation and bacterial activity. The simulator looks at bacterial growth both in planktonic and sessile forms. Monod kinetics is applied for the growth of bacteria, leading to the consumption of sulphate and volatile fatty acids which in-turn is linked to H2S generation. Along with H2S propagation, H2S scavenging by rock and H2S partitioning between the various phases is also accounted for. The model can also deal with the effects of lift gas, reinjection of sour produced water, injection of biocide and nitrite. Since the Field X is a green field and historical production data is unavailable, the model is calibrated against the provided field development plan (FDP) data with sensitivity analysis. The simulation runs show that the H2S breakthrough occurs before the end of production. The amount of H2S produced indicates that the risk of reservoir souring associated with seawater injection in U and L Reservoirs of the Field X is high. It is recommended to evaluate different reservoir souring preventive measures in combination with mitigative options in terms of chance of success, risks, and cost (CAPEX/OPEX) in the context of the Field X development plan.

A High-Response Electrochemical As(III) Sensor Using Fe3O4–rGO Nanocomposite Materials

Nowadays, heavy metal ion pollution in water is becoming more and more common, especially arsenic, which seriously threatens human health. In this work, we used Fe3O4–rGO nanocomposites to modify a glassy carbon electrode and selected square wave voltametric electrochemical detection methods to detect trace amounts of arsenic in water. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed that Fe3O4 nanoparticles were uniformly distributed on the rGO sheet, with a particle size of about 20 nm. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) showed that rGO provides higher sensitivity and conductive substrates. Under optimized experimental conditions, Fe3O4–rGO-modified glassy carbon electrodes showed a higher sensitivity (2.15 µA/ppb) and lower limit of detection (1.19 ppb) for arsenic. They also showed good selectivity, stability, and repeatability.