Gas Field Production Research Articles

Method for determining the harmonic contribution of consumer installations based on the application of passive filters

AbstractThe paper presents a new method for estimating the contribution of distortion sources based on the application of passive harmonic filters. The method does not require the measurement of harmonic network impedance and is based on the measurement of harmonic currents of the grid, consumers and passive harmonic filters. Evaluation of the consumer contribution using a passive harmonic filter is necessary to select the parameters and connection points for harmonic reduction devices. A feature of the method is the correct determination of share contributions, regardless of background harmonic distortions. Based on this method, a single consumer can evaluate both the harmonic contributions of its own loads, even in the presence of background distortions, and the harmonic voltage distortions in the case of installing harmonic reduction devices. The research results are confirmed in laboratory conditions with various combinations of electrical loads connected both at the grid side and at the consumer side. For such conditions, the proposed method was compared with existing methods, among which are methods based on the measurement of harmonic voltage vectors, harmonic current vectors and active harmonic power. The application of the developed method was demonstrated using the example of a gas production field.

Optimization of tight gas reservoir fracturing parameters via gradient boosting regression modeling

In China, the exploitation of most unconventional oil and gas reservoirs is dependent on hydraulic fracturing, which is a key method employed when developing tight gas formations. Numerous scholars and field engineers, both domestically and internationally, have conducted extensive numerical simulations and physical experiments to study crack propagation and predict post-fracturing productivity in hydraulic fracturing. Although some progress has been reported in this regard, it is difficult to accurately predict the well productivity using mechanistic models owing to the vertical multilayered development of tight gas reservoirs. In this study, vertical fractured wells in a block of Sulige gas field were examined. The block relied on hydraulic fracturing to produce tight gases. However, as development progressed, the available reservoir environment deteriorated, large differences emerged between wells after fracturing, and the fracturing results did not meet the expectations. In this study, geological, construction, and generation data for this block that had been collected since 2007 were analyzed. After applying multiple machine-learning methods to filter outliers and fill in missing values, k-means clustering, classification enhancement, extreme gradient enhancement, and LightGBM algorithms were used to establish a regression model. The analysis results revealed that the regression accuracy of the cluster test set was as high as 70% and that the LightGBM model had the best regression effect among the 227 stripper wells in the block. After optimizing the fracturing construction parameters (fracturing fluid volume, proppant volume, liquid-nitrogen volume, and pumping rate), the average fracturing fluid and liquid-nitrogen volumes per well decreased, whereas the unit reservoir proppant and liquid-nitrogen volumes increased. The results also revealed that 182 wells showed an improved initial production capacity during fracturing. The average gas production index per meter increased by 22.04%. This approach enabled rapid and efficient production forecasting and construction optimization. Moreover, this represents a novel fracture design method that is applicable to onsite engineers in tight gas production fields in the Ordos region.

Effect of Aquifer Strength and Gas-cap Size on Oil Recovery Efficiency in Thin-Oil Rim

Recovering oil from thin oil rim reservoirs depends on some factors such as the gas-cap size, thickness of initial oil column, aquifer strength, permeability anisotropy (kV/kH), and rock and fluid properties. The arbitrary selection of these factors by researchers during investigation limits the systematic assessment of the influence of these factors on hydrocarbon recovery from thin oil rim reservoirs. This work investigated the effect of aquifer strength, gas cap size, and permeability anisotropy on hydrocarbon recovery, using design of experiment (DOE) as a tool in the systematic selection of some of the factors that influence hydrocarbon recovery. A static model of the base case oil rim was built in Petrel. Using Eclipse simulator, two other reservoir models having different gas cap sizes from the base case were built. Forty-eight simulation cases were generated using the result from the design of experiment (DOE). The aquifer model used is a Fetkovich analytical aquifer model, and the aquifer volume factors used for this investigation are 0.7, 1.0, 1.5 and 2.5, while the gas cap sizes (m-factor) used are 0.5, 1.0 and 2.0. The permeability anisotropy used are 0.01, 0.05, 0.10 and 0.40. Each simulation case was made to run for a period of twenty years (20years) and the results for the Field Oil Efficiency (FOE), Field Water Production Total (FWPT) and Field Gas Production Total (FGPT) were obtained and analyzed. It was found from this study that, the oil percentage recovery will increase as the gas cap size is decreased, while the percentage gas and water recoveries will increase as the size of the gas cap is increased for a thin oil rim reservoir. Again, for a thin oil rim reservoir with gas cap size of 0.50 ≤ m ≤ 2.00, percentage recovery of gas, oil and water will increase with aquifer volume. Also, based on the result obtained, a thin oil rim reservoir with small to moderate gas cap size (0.5≤ m≤1.0) will yield higher oil recoveries irrespective of the kV /kH ratio.

DETERMINATION OF HYDROCARBON ZONE AND DEPOSITIONAL ENVIRONMENT FACIES IN TALANG AKAR FORMATION, SOUTH SUMATRA BASIN AT "EPURA" FIELD

The EPURA field is one of the oil and gas producing fields in the South Sumatra Basin, where well completion has been carried out in the Talang Akar Formation, and the production test results are interpreted to mean that in wells EP-13, EP-14, EP-15, EP-16, EP-17 and EP-23 contain several reservoir zones that have the potential to contain hydrocarbons. This research with facies interpretation analysis uses data from six wells (wireline, mudlog, RCAL and lithology data), so it is hoped that it can provide more detailed information for the development of an oil and gas field. The analysis carried out is in the form of facies analysis, depositional environment, electrofacies and facies correlation. From the research results, it was found that the Talang Akar Formation has depositional facies in the form of a fluvial, which in this study is the Lower Talang Akar Formation with depositional facies in the form of channel, Crevasse Splay, point bar and flood plain. Based on the analysis results, the Talang Akar Formation is divided into 3 reservoir zones, namely Zone EP-1, EP-2, and EP-3. After going through all stages of petrophysical analysis, it was found that zones with high hydrocarbon potential were found in wells EP-13, EP-23 and EP-16. The wells with low hydrocarbon potential are EP-14, EP-15 and EP-17 wells. The zone of highest hydrocarbon potential in prospect wells is in the EP-1 zone with a Crevasse Splay facies association and has thick sandstone lithology characteristics with medium to fine grain size.

Chemical Risk Assessment and Prevention Action Plan Related to Petroleum Production. Case Study of Laboratory and Storage Units in an Algerian Oil and Gas Company

Chemical risk is considered one of the most frequent risks in the workplace, affecting the safety of workers continuously exposed to chemical substances. In addition, it can have an environmental impact and cause an explosion when unacceptable conditions are met. To know the effects of chemical risks and how to prevent them, this study is proposed, the main objective of which is the evaluation of chemical hazards and the proposal of an action plan to avoid this kind of risk in industrial companies. Our case study focused on the crude oil production company " PERTAMINA" using the SEIRICH software. The results indicate that most chemicals are hazardous and can cause serious harm to workers exposed to them periodically. Therefore, the proposed preventive action plan for safety improvement aims to ensure continuous development in oil and gas field production, processing, and distribution, taking into account the health and safety of workers.

Topology-based 3-D fractal characterization of fracture complexity in propagation experiment

The complexity of the fracture network, formed by the interaction of hydraulic fractures and natural fractures during hydraulic fracturing, is one of the important criteria for guiding shale gas field production. In this study, we selected the deep shale of the Longmaxi formation as the object of study. Through indoor hydraulic fracturing experiments and fracture 3-D reconstruction technology, we conducted a quantitative study on the complexity of the fracture network created by the influence of hydraulic and natural fractures interacting with each other during hydraulic fracturing. The results show that the fractal dimensions, average connection numbers of topological structure branches, and relative lengths of fracture intersections for hydraulic fractures in 10 groups of specimens are 1.93-2.27, 0-1.143, and 1.02-1.98, respectively.

Horizontal borehole azimuth optimization for enhanced stability and coal seam gas production

Horizontal boreholes have been widely used to extract natural gas from coal seams. However, these boreholes can encounter severe instability issues leading to production interruption. Optimizing drilling azimuth is a potential solution for enhancing borehole stability while considering gas production. In this work, we improved and implemented a dual-porosity, fully coupled geomechanical-hydraulic numerical model into COMSOL Multiphysics to investigate into this factor. The sophisticated numerical model incorporates various critical factors, including desorption-induced matrix shrinkage, stress-dependent anisotropic fracture permeability, and the interactions of gas flow and reservoir deformation in matrices and fractures.A suite of simulation scenarios (e.g., varying coal strength) was carried out to quantify the impact of drilling azimuth on coal permeability evolution, cumulative gas production, and the borehole break-out width for Goonyella Middle Seam of Bowen Basin, Australia. The model was calibrated against both theoretical permeability values and field gas production data. Due to the lack of directly measured matrix permeability data, the actual gas production was used to back calculate the best-matched matrix permeability, which is 0.65 μD for this particular work. Moreover, based on the breakout shape and induced volumetric strains around the borehole, drilling along the maximum horizontal stress does not necessarily lead to the best stability of the borehole, as generally believed. A drilling azimuth between 0° and 60° results in similar breakout width, whereas a drilling azimuth between 60° and 90° achieves the most efficient gas production. By considering both gas production efficiency and borehole stability, for this particular reservoir condition, the optimum drilling azimuth is determined to be between 45° and 60°.This study presents a practical approach for determining the optimum drilling azimuth in coal seam gas extraction through in seam boreholes.

Neural networks informed by physics for modeling mass flow rate in a production wellbore

Optimal control strategies may efficiently manage and operate assets in contemporary oil and gas fields, lowering costs and maximizing yield. However, during this process, we encounter a traditional modeling challenge: obtaining an appropriate system representation. Concerning this task, the current research introduces a new hybrid model for simulating multi-phase mass flow in an offshore oil and gas production field. We investigate a concept based on Physics-Informed Neural Networks (PINN) to characterize the mass flow dynamics in a production wellbore. PINN models have been demonstrated as a feasible alternative for training neural networks using a small number of training data samples and estimating the parameters of physics equations that guide the underlying dynamics. The concept might provide alternatives to modeling and balancing the task of learning from physics and data in oil-gas systems. This research analyzes the performance of neural networks inspired by physics in a synthetic database constructed from the physics laws of mass conservation and conservation of momentum. After solidifying the principles, the study assessed the power of model assimilation in a real-world oilfield situation.

Influence of desorption hysteresis effects on coalbed methane migration and production based on dual-porosity medium model incorporating hysteresis pressure

Desorption hysteresis affects gas mass transfer and migration in coal seams, which is not considered in current dual-porosity medium models, leading to inaccurate assessment and prediction of gas extraction. This study proposed a desorption hysteresis pressure to address this issue of the gas mass transfer in the model. On this basis, two coupled gas migration models, considering (DGMH) and without considering (DGM) desorption hysteresis effects, were developed incorporating mass transfer, gas desorption, gas seepage, and permeability evolution. The models were solved and compared using the finite element method. The results demonstrate that the DGM model yields higher production assessment compared to the DGMH model. This discrepancy can be attributed to the hysteresis effects, which prevent the matrix gas from supplementing the fractures timely after fracture gas flows into the borehole. The DGMH model shows less mass transfer, coal seam permeability, and gas extraction compared to the DGM model. The desorption hysteresis effects are more pronounced in coal seams with higher permeability. In addition, neglecting hysteresis effects when calculating permeability from field gas production data may result in inaccurate values. The hysteresis effects is recommended to be considered in the prediction of coalbed methane extraction, permeability calculation, and risk control of delayed coal and gas outbursts.

Chemical Risk Assessment and Prevention Action Plan Related to Petroleum Production. Case Study of Laboratory and Storage Units in an Algerian Oil and Gas Company

Chemical risk is considered one of the most frequent risks in the workplace, affecting the safety of workers continuously exposed to chemical substances. In addition, it can have an environmental impact and cause an explosion when unacceptable conditions are met. To know the effects of chemical risks and how to prevent them, this study is proposed, the main objective of which is the evaluation of chemical hazards and the proposal of an action plan to avoid this kind of risk in industrial companies. Our case study focused on the crude oil production company " PERTAMINA" using the SEIRICH software. The results indicate that most chemicals are hazardous and can cause serious harm to workers exposed to them periodically. Therefore, the proposed preventive action plan for safety improvement aims to ensure continuous development in oil and gas field production, processing, and distribution, taking into account the health and safety of workers.

Evolution of acoustic methods for assessing and managing exposure of gray whales to sound pulses from seismic surveys off Sakhalin Island, Russian Far East

An effective program of estimation and mitigation of sound exposure from airgun array pulses is of vital importance when an endangered whale population forages in coastal waters near oil and gas production fields, where geophysical exploration campaigns regularly take place. Starting in 2001, increasingly sophisticated acoustic measurement and modeling techniques have been used for the environmental management of airgun array seismic surveys adjacent to the nearshore feeding grounds of the gray whale (Eschrichtius robustus) off the NE coast of Sakhalin Island, Russia. These monitoring data are also used in combination with visual observations for the analysis of the effects of sound exposure on whale behavior, distribution, and energetics. This talk follows two decades of evolution of the acoustic monitoring technology used in the Sakhalin studies, from rudimentary analog sonobuoys with limited bandwidth VHF telemetry, to digital stations capable of onboard signal processing and relaying of data via satellite to anywhere on the globe. In parallel, it traces the advancement of modeling techniques capable to fill the gaps between sparse measurement locations to yield high resolution estimates of the sound field from seismic sources operating concurrently at different, moving locations and in various regimes of ramp-up, production, or mitigation pulses.

An integrated workflow for seismic interpretation, petrophysical and petrographical characterization for the clastic Mangahewa reservoir in Pohokura gas field, Taranaki Basin, New Zealand

This research aims at delineating the main structural elements controlling the geologic setting of Taranaki Basin in New Zealand which in turn control the hydrocarbon potential of this basin and in particular of Pohokura Field which is considered one of the main gas-producing fields in the basin. This can be achieved utilizing the seismic data including three different marine seismic data sets covering 514.6 km2 with 12.5 m horizontal resolution. A synthetic seismogram and a set of seismic attributes were created to achieve this target. In addition, an integrated reservoir characterization study is applied to the Mangahewa reservoir in the Pohokura Field. This integrated characterization includes a detailed petrographical lithofacies analysis, well logging, and core analysis studies. Based on the petrographical study, eight lithofacies are described in Pohokura Field: 1) Laminated sandstone; 2) Massive sandstones; 3) Granular laminated sandstones; 4) Bioturbated sandstones; 5) Sand dominated and mud rich bioturbated sandstones; 6) Muddy bioturbated sandstone; 7) Laminated and rippled laminated mud rocks, and 8) Coal lithofacies which have been deposited in high energy shoreface setting. On the other side, the available well logging data includes caliper, GR (gamma-ray), sonic, neutron, density, and resistivity (shallow and deep resistivities). Logging interpretation enabled the estimation of the effective porosity (av. ∅ = 11.4%), hydrocarbon saturation (av. Shc = 62.87%), and the shale volume (av. VSh = 18.02%) with a total net pay thickness of all wells = 196 m. The available core data includes porosity, density, and permeability which are used to estimate the reservoir quality ranks; the effective pore radius (R35); the flow zone indicator, the discrete rock type (DRT), and the reservoir quality index (RQI). Considering the porosity, permeability, and the DRT values, the available core data are grouped into five reservoir rock types (RRTs) with the best reservoir quality assigned for the RRT1 (bioturbated, laminated and massive sandstones), while RRT5 has the lowest reservoir quality (muddy bioturbated sandstone, Granulated laminated sandstone, and laminated and rippled mudstone). This integrated study is applicable and extendable to the other basins in New Zealand and the southwestern Pacific. The proposed workflow is also applicable to the other analogs in the various basins elsewhere.

Theory, technology and practice of shale gas three-dimensional development: A case study of Fuling shale gas field in Sichuan Basin, SW China

In the Jiaoshiba block of the Fuling shale gas field, the employed reserves and recovery factor by primary well pattern are low, no obvious barrier is found in the development layer series, and layered development is difficult. Based on the understanding of the main factors controlling shale gas enrichment and high production, the theory and technology of shale gas three-dimensional development, such as fine description and modeling of shale gas reservoir, optimization of three-dimensional development strategy, highly efficient drilling with dense well pattern, precision fracturing and real-time control, are discussed. Three-dimensional development refers to the application of optimal and fast drilling and volume fracturing technologies, depending upon the sedimentary characteristics, reservoir characteristics and sweet spot distribution of shale gas, to form “artificial gas reservoir” in a multidimensional space, so as to maximize the employed reserves, recovery factor and yield rate of shale gas development. In the research on shale gas three-dimensional development, the geological + engineering sweet spot description is fundamental, the collaborative optimization of natural fractures and artificial fractures is critical, and the improvement of speed and efficiency in drilling and fracturing engineering is the guarantee. Through the implementation of three-dimensional development, the overall recovery factor in the Jiaoshiba block has increased from 12.6% to 23.3%, providing an important support for the continuous and stable production of the Fuling shale gas field.

Role of depositional and diagenetic controls on reservoir quality of complex heterogenous tidal sandstone reservoirs: An example from the Lower Goru formation, Middle Indus Basin, Southwest Pakistan

The Lower Goru Formation, one of the key hydrocarbon development targets in Pakistan's Middle Indus Basin, offers a unique opportunity to investigate the role of depositional and diagenetic controls on reservoir quality in complex stratigraphic traps. An integrated approach, including thin-section petrography, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), helium porosity, and permeability measurements, was used to analyze the Lower Goru Formation in three gas-producing fields. Based on petrographic interpretation, the sandstones are quartzarenite, sublitharenite, subarkose, and less commonly, litharenite. High permeability and high porosity reservoirs are associated with well-sorted and medium-grained sandstones. Main diagenetic processes include compaction, carbonate cementation, authigenic chlorite and quartz overgrowth. Authigenic chlorite, and quartz cementation were the principal reservoir quality controlling factors. Well-developed chlorite coatings preserved porosity and inhibited quartz cementation. Good quality reservoirs (average porosity: 17%; average permeability: 96 mD) are restricted to tidal channels and tidal inlet in the prograding shoreface environments. Transgressive and tidally reworked deposits show moderate porosity and very low permeability (average porosity: 9.5%; average permeability: 0.07 mD). Middle shoreface and bioturbated storm sands have low porosity and very low permeability (average porosity: 8.7%; average permeability: 0.9 mD) and are considered tight reservoirs. The quality of the studied reservoirs depends on quartz overgrowth, chlorite coating, carbonate cementation and minor detrital clay. Secondary porosity is associated with partial to complete dissolution of feldspar, volcanic rock fragments (VRF), biotite, chamosite ooids, and bioclast grains. This integrated work would be helpful for exploration and field development plans in the stratigraphic traps of the Middle Indus Basin and would lead to new exploration targets, i.e., tight and low permeability reservoirs. The study provides insight into the complex interplay between depositional facies and diagenesis in controlling reservoir quality in the Lower Goru Formation and similar depositional conditions and trapping mechanisms elsewhere.

Differential hydrocarbon generation and evolution of typical terrestrial gas-prone source rocks: An example from the Kuqa foreland basin, NW China

Terrestrial gas-prone source rocks are significant for hydrocarbon gas accumulations especially in central and western basins in China. The Kuqa foreland basin in the northern margin of the Tarim Basin, NW China is rich in natural gas with recent discoveries of several large to giant gas-producing fields (e.g., the Kela-2, Dibei, Dabei-1, and Zhongqiu-1 gas fields, etc.) and a proven 3 P gas reserve of over one trillion cubic meters (TCM). This proliferous petroleum province is powered by an effective and diverse gas-prone source rock series in the basin comprising mudstone, carbonaceous mudstone, and coal seams. To date, little systematic research work has been done on the petroleum generation potential of the source rocks. This has seriously restricted the assessment of petroleum resources and further exploration in the frontier areas of the basin. A sealed gold tube pyrolysis approach was employed to simulate the oil and gas generation and cracking yields for the aforementioned three types of source rock. Compared with typical Type I and II1 kerogens, the three types of source rocks in the Kuqa foreland basin are characterized by (1) far less hydrocarbon yield (150 mg/g TOC) with comparatively larger amounts of CO2 (310 mg/g TOC), (2) a limited capacity and narrower window (0.5%–1.08% Ro) for oil generation, and (3) a much earlier secondary cracking for bulk oil to light oil and gases (>0.86% Ro for mudstone and >1.08% Ro for both carbonaceous mudstone and coal). All the source rocks are gas-prone, and significant amount of gas can still be generated during an over-mature stage. The kinetic parameters obtained allow us to model hydrocarbon generation in the Kuqa foreland basin more realistically. It is concluded that (1) two episodes of hydrocarbon generation occurred with hydrocarbon gases being mainly generated during the later stage (12–3 Ma); and (2) the depocenter of the basin is capable of supplying massive high-mature gases as late as in the Quaternary, which is crucial for the formation of giant gas fields. The findings provide new insight on the reconstruction of oil and gas accumulation processes and further hydrocarbon exploration in the basin.

A declining trend of methane emissions in the Los Angeles basin from 2015 to 2020

The Los Angeles (LA) basin was responsible for approximately 20% of California’s methane emissions in 2016. Hence, curtailment of these emissions is required to meet California’s greenhouse gas emissions reduction targets. However, effective mitigation remains challenging in the presence of diverse methane sources like oil and gas production fields, refineries, landfills, wastewater treatment facilities, and natural gas infrastructure. In this study, we study the temporal variability in the surface concentrations from February 2015 to April 2022 to detect a declining trend in methane emissions. We quantify the reduction due to this declining trend through inverse modeling and show that methane emissions in the LA basin have declined by 15 Gg, or ∼7% over five years from January 2015 to May 2020.

Well production interference ratio in tight sandstone gas reservoir and its inspiration to well pattern optimization: a case study of Sulige gas field, NW China

In view of the characteristics of low permeability, strong heterogeneity, small effective sand scale and poor connectivity of tight gas reservoir, well pattern infilling optimization is the main method to improve gas recovery. Taking Sulige gas field as an example, based on the study of sedimentary facies, effective sand-body distribution, combined with production performance and engineering parameters, the well control drainage was obtained. Meanwhile, the interwell connectivity and interference probability was qualitatively analyzed by interference well test, and the critical well spacing density was determined. In order to quantitatively reveal the gas grabbing degree at different well spacing density and determine whether the final cumulative gas production of gas wells with interference is economical and feasible, the evaluation index of "gas well production interference ratio (GWPIR)" was defined specifically, and the intersection plot of GWPIR relating to gas reserve abundance and well spacing density was draw. Different from the traditional method of well number interference probability, through the combination of GWPIR plot and economic evaluation, well pattern optimization from both two perspectives of pursuing higher economic benefits and recovery degree can be realized, providing technical support for improving gas recovery and long-term stable production of gas field.

Ecological Insurance of Arctic Oil and Gas Producing Shelf Projects in Russia

The article deals with problems of ecological insurance of arctic oil and gas producing shelf projects in Russia and possible ways of its development. The authors put forward the method of estimating financial security of operations on eliminating possible ecological damage in case of hydrocarbon spill on arctic shelf oil and gas producing fields and study oil spills on arctic shelf fields ‘Prirazlomnoye’ and ‘Pobeda’. They estimate the cost of measures aimed at elimination of such incidents and propose a special indicator, i.e. financial loss factor for oil spill. Empiric conclusions obtained by comparative analysis of legislation in the field of ecology of entrails use in Russia, Norway, the US and Canada can be used for optimization of the effective Russian legislation and introduction of obligatory ecological insurance. Data of mathematic spill modeling can be applied by insurance companies for calculating insurance premium, by Rosprirodnadzor – for charging penalties and for other supervision bodies – for underwriting oil and gas arctic projects.

Global layout optimization of star-tree gas gathering pipeline network via an improved genetic optimization algorithm

Gas gathering pipeline network system is an important process facility for gas field production, which is responsible for collecting, transporting and purifying natural gas produced by wells. In this paper, an optimization model for the layout of star-tree gas gathering pipeline network in discrete space is established to find the most economical design scheme. The decision variables include valve set position, station position and pipeline connection relation. A series of equality and inequality constraints are developed, including node flow balance constraints, pipeline hydraulic constraints and pipeline structure constraints. A global optimization strategy is proposed and an improved genetic algorithm is used to solve the model. To verify the validity of the proposed method, the optimization model is applied to a coalbed methane field gathering pipeline network in China. The results show that the global optimization scheme saves 1489.74×104 RMB (26.36%) in investment cost compared with the original scheme. In addition, the comparison between the global and hierarchical optimization scheme shows that the investment cost of the global optimization scheme is 567.22×104 RMB less than that of the hierarchical optimization scheme, which further proves the superiority of the global optimization method. Finally, the study of this paper can provide theoretical guidance for the design and planning of gas field gathering pipeline network.

U-Pb detrital zircon geochronology of the Middle to Upper Jurassic strata in the Surat Basin: New insights into provenance, paleogeography, and source-sink processes in eastern Australia

New U-Pb detrital zircon ages from sandstones have been determined for the Walloon Coal Measures-Springbok Sandstone section of the Surat Basin. In the late Jurassic Surat Basin, there is a shift from relatively thick coal measures – the Walloon Coal Measures – consisting of laterally discontinuous coal-seam horizons intercalated with lithic sandstones and mudstones to an overlying coal-poor sandstone-dominated unit – the Springbok Sandstone – that is more laterally continuous. Across the basin, the contact between the two units varies from transitional to unconformable, and the sandstone becomes less lithic. The nature of the contact and the compositional variability of the sandstone across the basin have implications for predicting communication between gas production fields and potential aquifers in the Walloon Coal Measures and overlying Springbok Sandstone. This study tests whether detrital zircon age (LA-ICP-MS) populations from sandstones within these two units can identify provenance shifts and potential tectonic drivers for basin infill at this time. Detrital zircon ages of both units, informed by paleocurrent measurements showing a southerly flowing depositional system, suggest sediment was sourced from three distinct terranes: the Thomson Orogen in northeastern Queensland; Permian-Triassic granitic intrusions emplaced within the northeast New England Orogen during the Hunter-Bowen Orogeny accretion event; and an inferred but now eroded Jurassic magmatic-arc located along the eastern margin of Gondwana. Two major source-delivery systems, named here Western and Eastern Source systems, are recognized by distinct detrital zircon age populations in both formations in the northern Surat Basin. The Western Source of the Walloon Coal Measures delivered substantial Jurassic age zircons, with minor Pre-Cambrian input; the Eastern Source delivered substantial reworked Precambrian and lesser Jurassic zircons. In contrast, the Western Source of the Springbok Sandstone delivered substantial Jurassic and distinct Triassic zircons dated between ca 234 Ma and 224 Ma in the north-west, while the Eastern Source delivered more pronounced Pre-Cambrian input, with minor Jurassic and absent or minor age zircons in the northeast. Maximum depositional ages for the Springbok Sandstone are approximately 2 Ma younger in the northwestern than in the northeastern Surat Basin. The westward younging could be due to migration of the system and/or differential movement on the bounding faults.