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Research on the Ground Pressure Features of Long Wall Top Coal Caving Working Face in Extra-Thick Coal Seam
Ma Zhanyuan,
Liu Chuang,
Li Huamin
Issue:
Volume 9, Issue 2, March 2021
Pages:
12-16
Received:
24 March 2021
Accepted:
6 April 2021
Published:
21 May 2021
Abstract: Based on the raw data of shield pressure and overlying strata movement measured in the field, the ground pressure features and overlying strata movement were analyzed in 8202 extra-thick coal seam longwall top coal caving working face of Tongxin coal mine after its extraction. The research results show that: during the process of mining, the interval of the lower sub key strata caved for the first time is 120 m, the periodic weighting interval ranges from 15 m to 30 m, with an average of 25 m. When the immediate roof is relatively thick, the fractured lower sub key strata can be hinged to form a stable “Voussoir Beam” structure, which makes the ground pressure not severe and the shield pressure small in the ends of the panel. When the immediate roof is thin, the arc triangular of the lower sub key strata in the ends of the panel loses mechanical contact to the caved immediate roof and assumes a “Cantilever Beam” structure, which makes the ground pressure severe and shield pressure large in the ends of the panel. Due to the large mining space of longwall top coal caving working face in extra-thick coal seam and big rotary angle of the overlying strata, the lower sub key strata can’t connect with each other to form a stable bearing structure, therefore, the shield pressure is a given load of roof rock, which results in a constant pressure of the shield.
Abstract: Based on the raw data of shield pressure and overlying strata movement measured in the field, the ground pressure features and overlying strata movement were analyzed in 8202 extra-thick coal seam longwall top coal caving working face of Tongxin coal mine after its extraction. The research results show that: during the process of mining, the interv...
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Development of Domestic Gas Supply and Utilisation Prices for Effective Gas Distribution in Nigeria
Kenneth Nduka,
Ubanozie Julian Obibuike,
Ifeanyi Michael Onyejekwe,
Anthony Kerunwa,
Stanley Toochukwu Ekwueme
Issue:
Volume 9, Issue 2, March 2021
Pages:
17-23
Received:
7 May 2021
Accepted:
27 May 2021
Published:
16 June 2021
Abstract: Every resource produced by a country should by necessity satisfy the needs and demands of its populace before consideration is made for export. This will ensure that a country is sufficient in production and allocation of its resources. While Nigeria is regarded internationally as a major gas producer in the world, her local consumption of natural gas is limited due to unavailability of gas for domestic utilisations fuelled by large margins between domestic and international pricing of natural gas. At the international markets, the gas attracts higher price due to market conditions while the prices are relatively lower at the domestic level probably due to limited routes of utilisation of the resource. Because of this, gas producers prefer to sell their commodity at the international market creating scarcity at the local levels. This has heralded underdevelopment of the manufacturing sector and indigenous companies in Nigeria that thrive on natural gas. This situation can be ameliorated by developing a gas price model for effective utilization and distribution of gas in Nigeria. The model will determine the optimum price that producers should sale their gas to make profit and also make gas available locally. In this study, emphasis is made on the development of a domestic gas supply and utilisation price model for effective gas distribution in Nigeria. The model incorporates the cost of producing a unit volume of gas by the gas producer, the energy value of the gas and the quantity of the gas demanded locally. The model is based on the gas produced, utilised, flared, domestic gas requirement and the aggregate price of gas produced for the various companies. Results show that the total revenue accruable from flare is $1.877B/yr which is higher than the total revenue accruable from DGSO deficit which is $0.595B/Yr. Thus, it is better that companies resort not to flaring. Analysis of the results also shows that companies are provided incentive by the model which closes gas deficit gap through a reduction in gas penalty price. Therefore, it serves as direct incentives to companies who meet with their DGSO. The results show that the gas deficit and flare penalty price has a direct impact on the flare penalty.
Abstract: Every resource produced by a country should by necessity satisfy the needs and demands of its populace before consideration is made for export. This will ensure that a country is sufficient in production and allocation of its resources. While Nigeria is regarded internationally as a major gas producer in the world, her local consumption of natural ...
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Simulation Studies on Determination of Displacement and Areal Sweep Efficiencies for Hot CO2 Flooding in Niger Delta Heavy Oilfield
Jackreece Denovan Abili,
Nkemakolam Chinedu Izuwa,
Ifeanyi Michael Onyejekwe,
Stanley Toochukwu Ekwueme
Issue:
Volume 9, Issue 2, March 2021
Pages:
24-35
Received:
12 June 2021
Accepted:
24 June 2021
Published:
2 July 2021
Abstract: Recovery efficiency is very important in enhanced oil recovery (EOR) processes as it helps in the planning, design and selection of EOR methods that will be technically and economically feasible. In this study, Simulation on hot CO2 flooding is conducted using data from Niger Delta heavy oil reservoir. The compositional simulation process was carried out in ECLIPSE 300 compositional oil simulator. The recovery efficiency and injection calculations were modeled and simulated in Matlab. Numerical equations enabled the determination of the residual oil saturation and the consequent calculation of the injection and recovery before and after solvent breakthroughs. CO2 of 0.095cp viscosity was injected at pressure of 3500 psia and 200°F to heat up the reservoir at payzone and reduce the viscosity of the reservoir oil at in-situ reservoir condition. The reservoir oil initially at 14.23cp at initial reservoir temperature and pressure was heated and reduced to a viscosity of 2cP making the oil mobile and amenable to flow. Results show recovery of the process before and after breakthroughs. CO2 breakthrough was realized after 221 days of the flooding process. Of the 2461.2 ft distance from the injection wells to the producer well, CO2 reached only a distance of 100 ft at breakthrough. Out of the 2.77 PV total volume of CO2 injected in the flooding process, 0.1222 PV of CO2 was injected as at breakthrough. The recovery efficiency result show that the displacement efficiency at CO2 breakthrough and at the end of the flooding process are 15.17% and 78.63% respectively while the areal sweep efficiency at CO2 breakthrough and at the end of the flooding process are 44.02% and 93.32% respectively. The low displacement and areal sweep efficiency at breakthrough were due to early breakthrough of CO2 which did not allow sufficient period of time for the CO2 to contact considerable portions of the reservoir given its viscous nature. Furthermore, at CO2 breakthrough time, the injected hot CO2 had no sufficient time to soak the reservoir and reduce the viscosity of the oil; as such only a small fraction of the in-situ oil became mobile. An overall recovery efficiency of 73.33% realized in the flooding process signifies favourable flooding design hence is recommended for the development and recovery of Niger Delta heavy oilfield.
Abstract: Recovery efficiency is very important in enhanced oil recovery (EOR) processes as it helps in the planning, design and selection of EOR methods that will be technically and economically feasible. In this study, Simulation on hot CO2 flooding is conducted using data from Niger Delta heavy oil reservoir. The compositional simulation process was carri...
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