Large Natural Gas Research Articles

Perforation and Flowback Highlights From the Gorgon Field, Offshore Australia

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 182420, “Perforation and Rig Flowback Highlights for the Gorgon Field Development Wells,” by A.K. Morrison, SPE, and J.P. Beinke, SPE, Chevron Australia, prepared for the 2016 SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, 25–27 October. The paper has not been peer reviewed. The Gorgon liquefied-natural-gas project (Fig. 1) is one of the world’s largest natural gas projects and the biggest single resource development in Australia’s history. In 2014, eight Gorgon wells were perforated successfully, intercepting between three and seven commingled zones and gross intervals of up to 500 m per well. This paper contrasts the detailed perforating and flowback plan with the results of the operation where a number of planned, and some unplanned, contingencies were faced. Perforation Basis of Design The main element of the Gorgon- project well design that affected perforating was that reservoir sections would be completed with a cemented 70-in. liner in 8¾-in. open hole, with the top perforation approximately 250 m below the liner top. Each well was to be completed in multiple formation zones, with the average gross perforation interval per well (top to bottom shot measured distance) expected to be more than 400 m and an average net perforation interval (sum of perforated zones) of close to 150 m. Four perforating alternatives were evaluated with respect to their relative operational and subsurface risks: Tubing-conveyed perforating (TCP) shoot and drop—guns deployed into the liner on a gun hanger before upper completion is run and then fired and dropped after perforation TCP shoot and pull—a separate drillpipe-conveyed perforation trip before completion with use of a sized kill pill after perforation to mitigate losses before the upper completion is run Coiled-tubing conveyed Wireline conveyed After analysis, the TCP shoot-and- drop option was eliminated because of the additional time and well-control risk of drilling the required rathole to accommodate dropped guns. Shoot and pull was not considered a viable option because of a lack of a temperature-rated, post-perforation kill pill. Coiled tubing was rated feasible but with inherently greater operational risks when performed from a mobile offshore drilling unit. The process concluded that the wireline-conveyed method was the best solution despite requiring several perforating runs per well. Operational issues associated with this technique were identified, and plans were developed for these to be managed safely. The gun length per trip was expected to be approximately 30 m, necessitating at least five wireline trips to perforate each well, with each run expected to take between one and two rig shifts. In the event of failure (e.g., unsuccessful cable development), the selected contingency method for deployment was coiled tubing, which was considered a proven alternative.

Politics of Oil and Natural Gas vis-à-vis the Foreign Policy of Iran

:This study discusses the relationship of Iran’s oil and gas resources with its foreign policy. Because these resources play a major role in government power, they serve as a major focus of Iran’s governmental policy and relations with other countries. Our review led us to conclude that despite Iran’s abundant reserves – the world’s fourth-largest crude oil and largest natural gas reserves-international powers influenced the country’s foreign policy sufficiently for Iran to decrease its oil production. The authors will demonstrate how fluctuations in oil and natural gas production were the outcome of a globalized structure that affected instability in Iran’s foreign policy in specific ways. Our conceptual investigation of energy politics after the 1979 revolution revealed different policies that caused numerous concerns for the new government. While Iran’s politicians strove to retain the Islamic Republic above all, both doctrine and foreign policy revolved circuitously from a radical 1979 Revolution position to renewed radical position in 2005 with two intermediate shifts in position. One was pragmatic shift in the late 1980s, and the second took a more moderate tone in late 1990s by focusing almost entirely on the production of oil and natural gas.

Membrane Separation of CO2 from Natural Gas

Background: Raw natural gas, one of the most important fuel sources worldwide, contains high level of CO2, which must be removed to avoid problems like pipeline corrosion, compression cost and reduction of heating value. The three main technologies used to separate CO2 from natural gas include cryogenic distillation, amine absorption and membranes. Membrane technologies have various advantages especially for offshore platforms. In recent years, more and more membrane systems have been applied to large offshore natural gas upgrading projects. Two entirely different membrane processes can be applied to the separation of CO2 from natural gas: gas permeation membranes and membrane contactors. Keywords: CO2 separation, gas permeation membrane, membrane contactors, membrane plasticization, membrane technology, natural gas, pre-treatment systems.

Accumulation and potential analysis of self-sourced natural gas in the Ordovician Majiagou Formation of Ordos Basin, NW China

Abstract The characteristics of the marine carbonate source rocks and the accumulation and potential of self-sourced natural gas in the Ordovician Majiagou Formation of the Ordos Basin are investigated based on recent exploration by using geochemistry and gas-source correlation methods. Massive source rocks are developed around the salt depression, east of the paleo-uplift in the Ordovician Majiagou Formation during the Caledonian; and the natural gases produced by argillaceous dolomite and dolomitic mudstone are the major contributors of the Ordovician gas field. Besides widespread carbonate weathering crust reservoir, internal grain band dolomite reservoir are also well-developed in the Majiagou Formation, and both can act as favorable reservoirs. The natural gas of the Majiagou Formation is mainly self-sourced oil-type gas generated by in-situ source rock and accumulated near the source area. There is only limited local accumulation of natural gas produced in the upper strata and stored below. The Majiagou Formation around the salt depression has favorable conditions for large scale natural gas generation and accumulation, and has the advantage of collecting large area natural gas of self-generation and self-preservation. The frontier depression areas of the paleo-uplift to the west, north and south of Jingbian gas field are the potential Ordovician exploration targets in the future.

Understanding the lie of the land: an institutional analysis of petro-governance in Tanzania

Tanzania has recently discovered large petroleum and natural gas reserves, boosting its natural resource stocks and potential future revenue flows. Whether the country’s petroleum resources will translate into economic development will be determined by the institutions that the government puts into place to govern the petroleum sector, to include the legal institutions. This study reviews the most important provisions of the new legislative framework that the government has recently adopted to govern this newfound wealth. We examine the institutions and actors created by the legislation as well as the opportunities and challenges that may emerge in its future implementation. Specifically, we analyse the petro-sector institutions that the legislation creates and the types of authorities granted to them; the institutional constraints placed on authorities; the interaction between institutions; potential institutional overlaps, conflicts and gaps; and transparency and accountability mechanisms.

Petroleum systems of the deepwater Mozambique Basin

The Mozambique margin is relatively under explored with a small number of wells both onshore and offshore. Nine major gas fields have been identified to date (Brownfield et al., 2012), which are believed to contain a combined more than 150 trillion ft3 of natural gas. The discovery of large natural gas fields in the Rovuma basin represents one of the most exciting exploration successes of recent years and Mozambique is now considered to be a prolific hydrocarbon province (Hollebeek et al., 2015). This exploration study utilizes a modern, regional 2D seismic grid that was acquired in 2013 and processed to depth in 2015. It covers a large proportion of the Mozambique offshore province (Figure 1) and was used to assess hydrocarbon prospectivity in the region. Seven mega-sequences were identified based on stratigraphy from well ties (Uzcategui et al., 2014), the regional geology and seismic character and were interpreted throughout the study area. This interpretation provided a basin-scale, structural framework in which to model the petroleum systems. Structural and stratigraphic plays were mapped, assessed and built into a 3D model that assesses the viability and quality of petroleum systems offshore Mozambique.

The Future of Russian Gas Exports

Disputes between Russia and Ukraine over the terms for gas transit and deliveries prompted Russia to accelerate development of new gas pipelines to Europe circumventing Ukraine, as well as exploring the potential for gas export to additional markets like Turkey and China. The current paper examines implications of Russia increasing its gas exports capacity by building Nord Stream 2 (to Germany), Turkish Stream (to Turkey and Greece) and Power of Siberia (to China). We find that these projects have moderate effect on Russian gas exports and also that the impact on the European natural gas market is minor. We have also examined the impact of new Russian export pipes if subsidies to large Russian natural gas consumers are halved, or there are no sales to, or transit via, Ukraine. We find that the effects of increased export capacity are much stronger in these cases. The main policy implication of our study is that the EU and Russia have common interest in supporting further integration of European markets, although for somewhat different reasons. Russia wants to sustain, or increase, its exports to Europe, whereas the EU wants to make sure that the market functions well and that no country becomes vulnerable to pressure from Russia.

Measuring the Methane Leaks to the Air from Three Large Natural Gas Production Regions

Measuring the Methane Leaks to the Air from Three Large Natural Gas Production Regions

Investigation on the permeability characteristics of bedded salt rocks and the tightness of natural gas caverns in such formations

In China, the salt formations close to the lower reaches of the large natural gas routes and the main gas consuming regions are all bedded structures. The presences of non-halite or low-halite mudstone interlayers and interfaces (salt-interlayer) in these bedded salt formations increase the concern on the tightness of the natural gas caverns constructed in such formations. Therefore, different lithotypes of samples of bedded salt rocks have been prepared to determine their gas permeability evolution by steady-state and transient pulse-decay methods. The results show that the permeability of the samples is very low, within the range of 10−17 to 10−21 m2 after well compacted. The permeability of the interface is comparatively the highest, steadily around the order of 10−17 m2. A similar tendency of reducing permeability as deviatoric stress increases is found for all the samples; and unexpectedly there is no dilatancy and consequently steep increase of the permeability for all samples, even under very high differential stress. SEM (scanning electron microscopic) testing, as a supplement of tightness assessment, shows tight microstructure of all the bedded salt rocks cores. The experimental results indicate favourable performances for the tightness of natural gas caverns in such formations. Gas seepage around a gas cavern in such bedded salt formation was simulated by the FLAC3D software over a lifespan of 30 years. The results present that the interfaces act as the main channels for the gas to seep through. But the seepage distances in the vicinity of the cavern are so short that it causes a little influence on the tightness. Several factors, e.g., the internal gas pressure, the locations of interface, as well as the permeabilities of the interlayers were analyzed to investigate their effects on the tightness of a gas cavern. On the whole, the bedded salt rocks have enough low permeability and satisfactory tightness for the natural gas caverns constructed in.

Alarm management practices in natural gas processing plants

In industrial data sets, groups of variables often move together. Monitoring all these variables may result in many nuisance alarms. However, it is possible to take advantage of redundant information to design and reduce the size of alarm sets. The present work reports the application of an alarm management protocol based on alarm priorization to three large Natural Gas Processing Plants, during a three year period, and also investigates the use of different correlation analyses techniques as tools to assist in the further reduction of the number of alarms. The results show that the adopted practices enable the reduction of alarms.

Economic Impacts of Increased U.S. Exports of Natural Gas: An Energy System Perspective

With the recent shale gas boom, the U.S. is expected to have very large natural gas resources. In this respect, the key question is would it be better to rely completely on free market resource allocations which would lead to large exports of natural gas or to limit natural gas exports so that more could be used in the U.S.. After accounting for the cost of liquefying the natural gas and shipping it to foreign markets, the current price difference leaves room for considerable profit to producers from exports. In addition, there is a large domestic demand for natural gas from various sectors such as electricity generation, industrial applications, and the transportation sector etc. A hybrid modeling approach has been carried out using our version of the well-known MARket ALlocation (MARKAL)-Macro model to keep bottom-up model richness with macro effects to incorporate price and gross domestic product (GDP) feedbacks. One of the conclusion of this study is that permitting higher natural gas export levels leads to a small reduction in GDP (0.04%–0.17%). Higher exports also increases U.S. greenhouse gas (GHG) emissions and electricity prices (1.1%–7.2%). We also evaluate the impacts of natural gas exports in the presence of a Clean Energy Standard (CES) for electricity. In this case, the GDP impacts are similar, but the electricity and transport sector impacts are different.

Genetic types and accumulation models for biogenic gases in Bohai Bay Basin, eastern China

Abstract Bohai Bay basin, in eastern China, is rich in oil resources, but recently large natural gas accumulations have been found, mainly in Miocene reservoirs, at depths shallower than 1500 m. Molecular and stable carbon isotopic gas compositions show that the gases have several distinctive biogenic origins. The first type of biogenic gas is generated in anaerobic environments from thermally immature organic matter and this type of gas accumulates typically in reservoirs interbedded within the immature source rock succession. The second type occurs up dip or above heavy-oil reservoirs and the gas is inferred derived from crude oils in shallow reservoirs as a biodegradation product. The third type originates from source rocks that were buried deeply previously (>2800 m in the basin), where they were “geopasteurized”, but which are now uplifted and recolonized by microbes at their current shallow depths. The first type is generally referred to as primary biogenic gas. The second type is commonly referred to as secondary biogenic gases elsewhere, but herein is called biogenic gas from biodegraded oil (BG-BO). This distinguishes them from the third type which is described herein as secondary biogenic gas and which is distinguished from BG-BO. Bohai Bay Basin gas pools often contain one of the three biogenic gas types and are often mixed, more or less, with thermogenic natural gas from petroleum pools in Eocene reservoirs. It is therefore important to distinguish the genetic affinities of the biogenic natural gases as an aid to the development and exploration for additional biogenic gas resources in Bohai Bay Basin.

Probabilistic modeling of shale gas containment pits for environmental and safety management

ABSTRACTThe Marcellus Shale formation contains large natural gas reserves, which are increasingly being extracted using horizontal drilling techniques. Concerns about environmental effects have prompted studies regarding Marcellus operations, including the safety of pits and impoundments containing frac fluids and freshwater. A subset of these structures in West Virginia was evaluated using a risk-based field data collection tool, which revealed recurring problems. A probability-based method was developed to determine the likelihood of these problems occurring in larger sample sizes. Applying this method to portfolios of pits and impoundments would benefit the industry by identifying areas of improvement for construction and inspection.

Analysis of leaked LNG flow and consequent thermal effect for safety in LNG cargo containment system

As the large liquefied natural gas (LNG) carrier has emerged as an important LNG transportation, rigorous safety analysis of the carrier is required to achieve reliable technological solutions for safely transporting LNG. The present study uses numerical simulation (conjugate thermal analysis) to investigate LNG leakage and the consequent temperature change of the hull׳s steel plate in a LNG cargo containment system (CCS). To validate the numerical approach used in the study, experimental investigation on the temperature behavior of the hull׳s plate was conducted. The experimentally determined ductile-to-brittle transition temperature (DBTT) was used as the index of critical temperature for the hull׳s plate. A numerical simulation was used to estimate the behavior of cryogenic liquid in a porous structure in an LNG CCS and the resulting temperature change of the hull׳s plate due to LNG leakage under any filling conditions (various inlet pressures of leaking LNG and defect sizes). According to the numerical study, the thermal safety of the hull׳s plate is guaranteed in case where the LNG leakage hole is 2mm in diameter. The critical leakage hole size where temperature of hull׳s plate did not reach a DBTT lies between 2mm and 5mm under the leakage conditions.

Novel mixed fluid cascade natural gas liquefaction process configuration using absorption refrigeration system

In this study, a novel process configuration for large scale natural gas liquefaction process is introduced and analyzed. This configuration is based on replacement of vapor compression refrigeration cycle by absorption refrigeration system. The required heat duty in the absorption refrigeration system is obtained by available waste heat in the plant. Process simulation is done by Aspen HYSYS software which is a conventional chemical process simulator. Coefficient of performance of the ammonia- water cycle is 0.48. Specific power consumption of the introduced process is 0.172 kWh/kgLNG which shows 30% reduction in the power consumption. The required heat transfer area of the modified process can be decreased up to 31%.

Modelling and energy analysis of an integrated coal gasification and pyrolysis system for synthetic natural gas

The entrained-flow coal gasification is an important and attractive technology in large scale coal-based synthetic natural gas (SNG) process. In this study, an integrated entrained-flow coal gasification and pyrolysis system is proposed and investigated. The gasifier is divided into two stages in this system: one is mainly for the gasification of char and the other is mainly for the coal pyrolysis. The integrated system is studied by using a process simulation model and compared with a coal gasification system with the radiant and convective coolers. The effects of the operating conditions on the gasification performance are studied and the optimized operating conditions are obtained. It is found that the optimized steam coal ratio of the integrated system is about 250–300 kg(steam)/t (dry coal) while the gasification temperature is 1400°C. The cold gas efficiency of 88.18% of the integrated system is higher than that of 84.14% of the gasification and radiant+conductive cooler system. The coal and O2 consumptions are relative low in the integrated system. The performance of the integrated system is highly related to the yield of tar and CH4 in the pyrolysis stage. The overall energy conversion efficiency of the integrated system (92.26%) is slightly lower than that of the gasification and radiant+conductive cooler system (93.39%). However, the exergy efficiency is enhanced by more than 2.2% in the integrated system. The integration of the gasification and pyrolysis can effectively recover and promote energy grade of the sensitive heat in the hot syngas.

Natural gas pricing reform in China: Getting closer to a market system?

Recent policy in China targets an increase in the contribution of natural gas to the nation's energy supply. Historically, China's natural gas prices have been highly regulated with a goal to protect consumers. The old pricing regime failed to provide enough incentives for natural gas suppliers, which often resulted in natural gas shortage. A new gas pricing reform was tested in Guangdong and Guangxi provinces in 2011, and introduced nationwide in 2013. The reform is aimed at creating a more market-based pricing mechanism. We show that a substantial progress toward a better predictability and transparency of prices has been made. The prices are now more connected with the international fuel oil and liquid petroleum gas prices. The government's approach for a temporary two-tier pricing when some volumes are still traded at old prices reduced a potential opposition during the new regime implementation. Some limitations of the natural gas pricing remain as it created biased incentives for producers and favors large natural gas suppliers. The pricing reform at its current stage falls short of establishing a complete market mechanism driven by an interaction of supply and demand of natural gas in China.

Environmental and economic impact of the use of natural gas for generating electricity in The Amazon: A case study

The transformations taking place in the Amazon, considered the "lungs of the planet", have special significance, not only for energy savings, but also for its environmental impact due to the reduction of greenhouse gases. Since 2010, in Manaus, the capital of Amazonas in Brazil, many power plants are replacing fuel oil with natural gas for power generation. Because of the large natural gas reserves in the region, this fuel has become the best choice for power plants built in this place. This paper analyzes the technical economic and environmental impact of the substitution of fuel oil by natural gas in the analyzed power generation plant.

Kinetics and model of gas generation of source rocks in the deepwater area, Qiongdongnan Basin

In order to investigate the hydrocarbon generation process and gas potentials of source rocks in deepwater area of the Qiongdongnan Basin, kinetic parameters of gas generation (activation energy distribution and frequency factor) of the Yacheng Formation source rocks (coal and neritic mudstones) was determined by thermal simulation experiments in the closed system and the specific KINETICS Software. The results show that the activation energy (E a) distribution of C1–C5 generation ranges from 50 to 74 kcal/mol with a frequency factor of 2.4×1015 s−1 for the neritic mudstone and the E a distribution of C1–C5 generation ranges from 49 to 73 kcal/mol with a frequency factor of 8.92×1013 s−1 for the coal. On the basis of these kinetic parameters and combined with the data of sedimentary burial and paleothermal histories, the gas generation model of the Yacheng Formation source rocks closer to geological condition was worked out, indicating its main gas generation stage at R o (vitrinite reflectance) of 1.25%–2.8%. Meanwhile, the gas generation process of the source rocks of different structural locations (central part, southern slope and south low uplift) in the Lingshui Sag was simulated. Among them, the gas generation of the Yacheng Formation source rocks in the central part and the southern slope of the sag entered the main gas window at 10 and 5 Ma respectively and the peak gas generation in the southern slope occurred at 3 Ma. The very late peak gas generation and the relatively large gas potential indices (GPI: 20×108–60×108 m3/km2) would provide favorable conditions for the accumulation of large natural gas reserves in the deepwater area.

The Sun Doesn't Always Shine in Ohio: Reevaluating Renewable Portfolio Standards in Light of Changed Conditions

In 2014, with the signing of Senate Bill 310 (S.B. 310), Ohio became the first state to put a temporary “freeze” on its renewable portfolio standard (RPS) and energy efficiency mandates. The law has generated nationwide attention and been criticized as a step back in the state’s clean energy policy. This Note examines the central justifications for the passage of S.B. 310, challenging conventional wisdom that the law does not serve the interests of Ohio citizens. After the passage of Ohio’s RPS in 2008, the economic and energy landscape within the state changed dramatically, due in large part to technological advances allowing for the development of the state’s large natural gas deposits. In order to fully assess these changed conditions, as well as the economic impact the energy mandates were having on ratepayers, Ohio lawmakers passed S.B. 310. While renewable resource advocates argue that increased renewable energy benefits the state of Ohio, this Note argues that S.B. 310 was an example of prudent lawmaking and should serve as a model for other states that have undergone changes in their energy landscape and economic situation since implementing their renewable portfolio standards.