Analysis of the financial assurance problem for decommissioning of oil and gas wells and facilities

The harmful effects of oil and gas projects on the environment are not limited to the production period. Unlike operating production facilities, control over the state of abandoned wells and fields falls on the state. In the Russian Federation, the obligations of subsoil user companies to properly perform decommissioning operations are not legally regulated and financially secured. Based on world experience, the paper analyzes the most common schemes for formation and accounting of financial assurance for decommissioning operations and examines the state of legislative regulation on this problem in Russia and the world. It presents recommendations on state regulation to guarantee full completion of decommissioning operations by subsoil users, improve their quality and monitor the environmental safety of abandoned wells.

Condensate Banking Removal Using Slow Release of In-Situ Energized Fluid

Condensate banking represent a persistent challenge during gas production from tight reservoir. The accumulation of condensate around the wellbore can rapidly diminish gas production. When reservoir pressure drop below dew point, condensate start to dropout from gas phase, filling pores and permeable fractures, and block gas production. There are several strategies to mitigate condensate banking, however, these strategies are either demonstrate limited results or are economically not viable. In this study, a novel method to mitigate condensate was developed using thermochemical reactants. Slow-release of thermochemical reactants inside different core samples was studied. The effect of in-situ generation of gas on the petrophysical properties of the rock was reported. Thermochemical treatment was applied to recover condensate on sandstone and carbonate, where the reported recoveries were around 70%. However, when shale sample was used, the recovery was only 43%. Advanced Equation-of-State (EoS) compositional and unconventional simulator (GEM) from CMG (Computer Modelling Group) software was used to simulate thermochemical treatment and gas injection. The simulation study showed that thermochemical stimulation had increased production period from 3.5 to 22.7 months, compared to gas injection.

Cement Conundrum: Valuable Lessons Learned for Sustaining Production

Addressing wellbore integrity through cement evaluation has been an evergreen topic which frequently catches major operators by surprise due to premature water or gas breakthrough causing low production attainability from the wells. Managing idle well strings arising from integrity issues is also a challenge throughout the production period. The remedial solutions to these issues do not come conveniently and require high cost during late life well intervention which often erodes the well economic limit. A critical element of wellbore barrier which is cement integrity evaluation is proposed to be uplifted and given a new perspective to define success criteria for producer wells to achieve certain reserves addition and production recovery. This paper will highlight integrated factors affecting cement bond quality, impact to well production, potential remedies for poor cement bond observed leveraging on the enhanced workflow and new technology and way forward to proactively prevent the unwanted circumstances in the first opportunity taken. A set of recommendations and prioritization criteria for future cement improvement will be also highlighted. Several case specific wells logged with variable cement bond evaluation tools are re-assessed and deep-dived to trace the root causes for unsatisfactory cement bond quality observed which include reservoir characteristics, understanding anomalies during drilling and cementing operation, identifying cement recipe used, log processing parameters applied and observing best practices during cementing operation to improve the quality. New and emerging cement evaluation technology inclusive of radioactive-based logging to meet specific well objectives will be also briefly discussed in terms of differences and technical deliverables. Looking at each spectrum, results show that there are several interdependent factors contributing to poor cement bond quality observed. Accurate understanding of formation behavior, designing fit-for-purpose cement recipe and adequate planning for cementing operation on well-by-well basis are among the top- notch approaches to be applied for an acceptable cement bond quality and placement. Statistics show that 27% to 64% of production attainability is achieved by wells with good cement quality within the first 3 months of production and this increases to 85% to 98% up until 7 months of production period, while only 12% production attainability achieved for those wells with adverse cement quality issue. In another well, water cut as high as 47% since the first day of production is observed which keeps increasing up to 40% thereafter. In a nutshell, cement evaluation exercise shall not be treated as vacuum, instead it requires an integrated foundation and close collaboration to materialize the desired outcomes. Arresting the issue with the right approach in the first place will be the enabler for optimum well performance and productivity to exceed the recovery target.

Techno-Economic Analysis of Hydraulic Fracturing As A Solution for Developing Low-Resistivity and Low-Quality Zone on Offshore “RI” Field

Hydrocarbon production in Indonesia is continuously decreasing on a yearly basis, which is in contrast with its increasing level of consumption. Low-quality and low-resistivity reservoir zones are deemed to possess a lot of hydrocarbon potentials, however, little priority has been placed on their development due to their small level of production. The "RI" field that was utilized in this study is a mature offshore field with a reservoir which has a low-quality and low-resistivity zone. This area has been in use for more than thirty years, therefore its rate of oil production has declined. This study aims to review the techno-economic aspects of well stimulation in the form of hydraulic fracturing. And also, to determine the development method that is suitable for low-quality fields. The hydraulic fracturing process was modelled using Fracpro software as input parameters for the reservoir production simulations. The reservoir behavior was simulated using the CMG software to observe the amount of hydrocarbon liable for production in various development scenarios. Three cases were performed on the "RI" field, which was stimulated for ten years of operation. The first case was the instance with the natural flow, while the second implemented hydraulic fracturing at the beginning of production, and the third was the implementation of hydraulic fracturing, which started in the middle of the production period. Then, the three cases are evaluated utilizing a Gross Split scheme, to calculate the economics of the project both from the government and contractor's aspects. The simulation study concluded that fracturing at the beginning of the LRLC zone development is the most profitable. The novelty of this study is the comparison of scenarios for the implementation of hydraulic fracturing methods in fields with low-resistivity and low-quality zone whose economic value is evaluated by the Gross Split scheme.

Experimental study on production performance and reserves utilization law in carbonate gas reservoirs

Carbonate gas reservoirs in China are rich in reserves. In the development process, there are many reserves with low permeability, low efficiency and low recovery degree. It is difficult to stabilize gas well production and prolong its life cycle. Under the condition of original water saturation (Sw) of 0%, 20%, 40%, 55% and 65%, respectively, the physical simulation experiment of gas reservoirs depletion development was carried out by using long core multi-point embedded pressure measuring system. The long cores with average gas permeability of 2.300 mD, 0.485 mD and 0.046 mD (assembled from 10 carbonate cores) were used to carry out this experiment. During the experiment, the pressure dynamics at different positions inside the long core and the gas production dynamics at the outlet were recorded in real time to reveal the production performance and reserves utilization law of carbonate gas reservoirs. The results show that the stable production period of tight reservoir in carbonate gas reservoirs is short, and the low production period is relatively long. The stable production time and recovery rate of gas reservoir increase with the increase of reservoir permeability and decrease with the increase of water saturation. The production of tight carbonate gas reservoirs with permeability less than 0.1 mD is greatly affected by pore water, and the reservoir pressure distribution shows a steep pressure drop funnel, and the reserves far from well are rarely used. Therefore, the reserves far from well should be utilized by closing well to restore formation pressure balance, densifying well pattern or transforming reservoir. The variation range of water saturation in the development of carbonate gas reservoirs is influenced by reservoir permeability and water saturation, and closely related to formation pressure gradient in production process. It decreases with the increase of reservoir permeability and increases with the increase of original water saturation. The research results provide a theoretical basis for understanding the relationship between physical properties of carbonate gas reservoirs and production performance, reserves utilization law, and realizing balanced utilization, efficient development and long-term stable production of carbonate gas reservoirs.

Supplementary Light with Increased Blue Fraction Accelerates Emergence and Improves Development of the Inflorescence in Aechmea, Guzmania and Vriesea

In protected cultivation, increasing the light level via supplementary lighting (SL) is critical to improve external quality, especially in periods with low light availability. Despite wide applications, the effect of light quality remains understated. In this study, the effect of SL quality and nutrient solution electrical conductivity (EC) on growth and flowering of three bromeliad species was investigated. Treatments included solar light, and this supplemented with R90B10 [90% red (R) and 10% blue (B)], R80B20 (80% R and 20% B), and R70B30 (70% R and 30% B). These were combined with an EC of 1 and 2 dS m-l. Irrespective of the light treatment, the higher EC promoted growth, inflorescence emergence, and development in Aechmea fasciata (Lindl.) Baker, whereas adverse effects were noted in Guzmania and Vriesea. The higher EC-induced negative effect in Guzmania and Vriesea was slightly alleviated by SL. With few notable exceptions, SL exerted limited effects on photosynthetic functionality. Depending on the species, SL improved external quality traits. In all species, SL increased root and inflorescence weight and stimulated biomass allocation to generative organs. It also accelerated inflorescence emergence and promoted inflorescence development. In this way, the time to commercial development stage was considerably shortened. These effects were more prominent at R80B20 and R70B30. Under those conditions, for instance, inflorescence emergence occurred 3–5 weeks earlier than in the control, depending on the species. In conclusion, SL with increased B proportion leads to shorter production period owing to faster emergence and improved development of the inflorescence and is recommended for commercial use.

Environmental Aspects of Historical Ferromanganese Tailings in the Šibenik Bay, Croatia

The former manganese ferroalloy plant and the remaining tailings are affecting the quality of the environment in Šibenik Bay, Croatia, even though industrial activities ceased more than 25 years ago. This study has revealed that the main manganese mineral phases present in the recently collected tailings, as well as in the dust collected on the roof of the plant during the production period, are bustamite and Mn-oxides. The same type of Mn mineral phases was also found in recently collected sediments from Šibenik Bay. Detailed chemical and phase analyses (XRD, BCR sequential analysis, aqua regia and lithium borate fusion) of the dust sample revealed high manganese values (24.1%), while granulometric analysis showed that 50% of the particles are smaller than PM2.5. The influence of the tailings is visible in the sediment, but the concentrations of the potentially toxic elements determined by the sequential BCR analysis are within the legal limits. Some higher values (20.3 g/kg Mn, 595 mg/kg Pb and 494 mg/kg Zn) are detected in the tailings, which are still exposed to weathering and as such should be additionally monitored. On the other hand, this material contains a considerable number of elements that could be considered lucrative (∑ REE up to 700 mg/kg, Mn up to 23 g/kg, Fe up to 37 g/kg and Al up to 25 g/kg), opening the possibility of reuse and recovery.

The effect of dietary forages in tetanus hyper immunized equine serum production

The determination of local forage in meeting the nutritional requirement of horses and its effect on the antibody titer production is necessary to be conducted. The aim of the study was to determine the effect of dietary forage to antibody titer production of Anti-Tetanus Serum. All procedures performed in this study were approved by the Institutional Animal Care and Use Committee (Ethical Approval No: 01/IACUC-BF/VI/20). A total of 12 Sandalwood horses aged 3-6 years with body weight ranged at 268.4 - 365.8 kg were used in this study. Horses were randomly assigned into four dietary treatment groups for ten weeks (100% Elephant grass; 100% Mott elephant grass; 67% Elephant grass: 33% Kikuyu grass; and 67% Mott elephant grass: 33% Kikuyu grass) which allowed 7.24; 11.45; 11.12; 12.62% crude protein respectively. The titer measurement was carried out once a week during the production period. The data obtained was analyzed using correlation analysis. The results showed that 100% Mott elephant grass group produced the highest titer but the correlation between crude protein levels in the diets and titer were weak (0.44). Thus, it can be concluded that the high protein forage given has no potential to increase the serum antibody titer.

Potential of Spent Pleurotus ostreatus Mushroom Substrate as Compost

Oyster mushroom (Pleurotus ostreatus) cultivation produces waste in the form of mushroom substrate that has passed the production period and contaminated substrate. Non-productive spent mushroom substrates (SMS) still contain nutrients that allow them to be composted. The main goal of this study is to determine the potential of SMS as compost. The composting was done by mixing each of the old substrate waste (P1) and contaminated (P2) with a solution of EM4 and sugar. Temperature measurement and material compost stirring were done every week. The test results after 8 weeks of composting showed that the physical characteristics of compost, including the color and texture, have complied with the standards of SNI 19-7030-2004, which was brown and smooth. P1 compost has an earthy odor while P2 compost still has a slight woody. The mass of P1 and P2 composts decreased by 32% and 32,4%, respectively. Micronutrients such as Fe, Zn, and Mo were varied and according to SNI 19-7030-2004, Minister of Agriculture Regulations No.28/Permentan/SR.130/5/2009 as well as Minister of Agriculture Regulations No.70/Permentan/SR.140/10/2011. Co did not comply with the standard. The water content, pH, and macronutrients such as N-total, P2O5, K2O dan C-organic in both types of compost were according to SNI 19-7030-2004, Minister of Agriculture Regulations No.28/Permentan/SR.130/5/2009 or Minister of Agriculture Regulations No.70/Permentan/SR.140/10/2011. The C/N ratio in compost was still high, compost P1 and P2 had 25,26% and 25,16%. To reduce the C/N ratio of compost, it is necessary to carry out several treatments such as increasing the decomposition time or adding other organic materials during the composting process. The addition of organic materials such as manure or bran allows the microbial activators to be optimally in decomposing compost material to shorten the composting time.

Phenotypic and Molecular Characterization of Strains Lasiododulpodia theobromae (pat) Griffon & Maulk, Pathogen-Associated with Black Rot Cocoa Pods in the Tshopo Province, Kisangani Region (DR Congo)

The cocoa tree (Theobroma cacao L) is a persistent perennial crop in tropical regions whose production period is sufficiently spread out over the whole year. As a result, it offers pathogens conditions for survival without real disruption of their life cycle. Symptoms of cocoa pod black rot disease have been observed in both the Bengamisa cocoa growing area and the Yangambi area in the Democratic Republic of Congo (DRC). This study aimed to characterize the strains of Lasiodiplodia theobromae on cocoa trees in the Kisangani region. Macroscopic and microscopic observations were made on the pods while the identification of the species was confirmed by a molecular approach based on the sequencing of part of the ribosomal DNA including the ITS regions (internal transcribed spacers) and the 5.8S gene. The results of this study showed that the phenotypic characteristics of the strains isolated in the two cocoa growing areas were typical of the L. Theobromae species. These are in particular the spots of soft rot, initially brown, gradually evolving into soot-black which subsequently produced a sort of whitish powder on the surface of the diseased pod. However, the fruiting of the fungus in the PDA medium gave rise to the latter's mycelia, initially whitish, which darkened as they matured. In addition, PCR amplification followed by sequencing of the fungal strain was beneficial by removing any doubt about the nature of the fungal species isolated in the two cocoa-growing areas.