Understanding Mud Volcano System Using Hele-Shaw (H-S) Experiment: Seismic Confirmation at East Java Mud Volcano

Numerous researchers have carried out studies on the mud volcano system in East Java. However, there have been no experiments on the mud volcano system's mechanism, including overpressure confirmed by direct subsurface data. Therefore, this study aims to directly evaluate the mud volcano system's mechanism using the Hele-Shaw (H-S) experiment with the subsurface data confirmation. The H-S experiment utilized four primary materials: quartz sand diameter below 250 µm and 320 µm to analogize the porous layer. Gypsum flour clay is the ductile layer, while mud from the Kuwu and Kesongo Mud Volcanoes is the original material from nature. Wax represents impermeable material. The sealing layer is made of wax, and oxygen represents the natural fluids of the rock formation. The overpressured zone is created by pumping oxygen into a layer of quartz sand covered by a wax as an impermeable layer. Pressure is measured digitally, and the process is continuously recorded to produce traceable data. Each material was experimented on individually to determine the critical phase characteristics, valve fault structure geometry, and validation with seismic interpretation. The results indicate that the critical phase of the mud volcano system is characterized by the dome structure at the surface, with high intensify of gas and oil seepage. Piercement structure geometry is shown by plumbing of fluidization zone, which becomes shallower than before. Furthermore, each material's piercement structure geometry shows a consistent pattern, with differences in the density of the fault and pressure structures. Thus, the H-S experiment's validation with seismic interpretation shows a similar geometry in pressure structures and valve faults as the mud volcano system's migration paths.

Multi-horizon Simultaneous Tracking Based on Dynamic Seismic Waveform Matching

Summary Due to the rapid increase in the amount of seismic volumes, the traditional seismic interpretation mode based on manual structure interpretation and single-horizon automatic tracking has encountered many challenges. The seismic interpretation of large or super-large 3-D seismic surveys is facing serious accuracy and efficiency bottlenecks. Aiming to the goal of improving the accuracy and efficiency of seismic interpretation, we propose a dynamic seismic waveform matching technology based on the sparse dynamic time warping algorithm under the guidance of the relative geological time volume theory, and realize multi-horizon simultaneous tracking based on the technology. Has been verified by a model and a real seismic volume, it can realize simultaneous horizon automatic tracking, full spatial tracking and high-density tracking, and can significantly improve the accuracy and efficiency of structure interpretation.

First Case Study for Litho-Petro-Elastic AVA Pre-Stack Inversion for Complex Tight Reservoirs Miocene – Upper Cretaceous in East Onshore Abu Dhabi

This study summarizes the efforts taken to provide reliable reservoir characterizations products to mitigate seismic interpretation challenges and delineation of the reservoirs. ADNOC has conducted seismic exploration activities to assess Miocene to Upper Cretaceous aged reservoirs in East Onshore Abu Dhabi. The Oligo-Miocene section comprises of interbedded salt (mainly halite), anhydrite, limestones and marls. Deposited in the foreland basin related to the Oman thrust-belt. Ranging in thickness from nearly 1.5 km in the depocenter to almost nil on the forebulge located to the west of the studied area. The well data based geological model suggests that initially porous rocks (presumably grain-supported carbonates) encompassed polyphase sulfate cementation during recurrent subaerial exposure in which pores and grains were recrystallized sometimes completely too massive, tight anhydrite beds. This heterogeneity of the complex shallow section showing high variation of velocity impact seismic imaging, and interpretation to model the stratigraphic/structural framework and link it with reservoir characterization. Hence, ADNOC decided to conduct a trial on state-of-art technique Litho-Petro-Elastic (LPE) AVA Inversion to mitigate the seismic interpretation challenges and delineate the reservoirs. The LPE AVA inversion provides a single-loop approach to reservoir characterization based on rock physics models and compaction trends, reducing the dependency on a detailed prior the low frequency model, Where the rock modelling and lithology classification are not separate steps but interact directly with the seismic AVO inversion for optimal estimates of lithologies and elastic properties. The LPE inversion scope requires seismic data conditioning such as CMP gathers de-noising, de-multiple, flattening and amplitude preservation, in addition to detailed log conditioning, petro-elastic and rock physics analysis to maximize the quality and value of the results. The study proved that the LPE AVA Inversion can be used to guide seismic interpreters in mapping the structural framework in challenging seismic data, as it managed to improve the prospect evaluation.

Depositional Processes of the Cenomanian-Turonian Reworked Carbonates in the Eastern Abu Dhabi, UAE

There are a limited number of studies and exploration cases for a "reworked carbonate" in Abu Dhabi, although these sediments are composed from some large oil and gas fields around the world (e.g. Poza Rica oil field in Mexico and Ruby gas field in Indonesia). In this study, we focused on Cenomanian-Turonian carbonates and considered the depositional processes of a "reworked carbonate" in the eastern part of Abu Dhabi. To understand the stacking pattern and/or depositional process of the Cenomanian-Turonian carbonate, we conducted a well-well correlation for total 16 wells, based on the core observations, wireline logs correlation (GR, Neutron, Density, Resistivity and Sonic), carbon and oxygen isotope analysis and trace elements analysis. Sampling was conducted for 8 wells and samples were taken approximately every 5 ft. In addition, to predict the spatiotemporal expansion of the reworked deposit, a 3D seismic interpretation was conducted. The result of the well-well correlation reveals that the depositional process and the stacking pattern of the Cenomanian-Turonian shoals around eastern Abu Dhabi are well consistent with the depositional model that proposed by Razin et al., 2010, and the reworked deposits are developed around the distal environment. 3D seismic interpretation represents that these reworked sediments were input from the north-west side and spread to the south-east like as a submarine-fan. Considering the core observation result, cohesive debris flow deposits are dominated at the depositional up-dip side and dilute flow deposits are dominated in the depositional down-dip side. In addition, an obvious erosional surface can be recognized in seismic sections and it truncates the top shoal sediments. The result of both, a combination of localized up-rift and global eustatic sea level fall in the early-middle Turonian triggered the regional erosion which is recognized as the middle Turonian unconformity. The result of this study suggests that the shoal sediments were eroded and reworked to a more distal environment at the early-middle Turonian.

Application of Spectral Decomposition Technique to Delineate the Evolution of Karst on Carbonate Platforms of Central Luconia, Offshore Sarawak, Malaysia

Karstification in carbonate platforms of the Miocene age in Central Luconia province, offshore Sarawak, Malaysia, has been discussed since the onset of exploration and initial discoveries in the region, with over 200 mapped platforms to date. An extensive drilling program over the last decade confirmed the existence of karst during the drilling process where issues such as total loss circulation and bit drops were common. Karst in Central Luconia has been proposed by several authors; however, detailed quantitative description of the observed features have not yet been conducted. This study involves systematic mapping of loss circulation depths, chalkified/rubble/vuggy zones described from cores, and vugs of >2 mm in size and moldic porosity observed on thin sections of the Jintan platform. These data supplement the interpretation of karst from multiple 3D seismic attributes. Seismic interpretation of the Jintan and M1 platforms revealed an extensive dendritic pattern which is on average 70–100 m deep and 3–5 km long, and circular geobodies of 1 km in width that exist on the upper part of the platform. Spectral decomposition, also known as time-frequency analysis, was used to enhance the interpretation of karst features on seismics within a specific wavelength. In this study, a comparison of three spectral decomposition methods applied on the 3D seismic cube of the Jintan and M1 platforms was undertaken to determine the method which allowed for better delineation of the karst features. The results show that the short-time Fourier transform (STFT) method using frequencies of 46, 54, and 60 Hz delineated most of the karst features compared to the continuous wavelet transform (CWT) Morlet and CWT Ricker wavelet methods. This paper aims to discuss the dimensions, evolution and geometry of the karst features quantitatively on three selected karst horizons named “K1”, “K2”, “K3”. Interpretation revealed that the dendritic karst features were found to be most prominent on the K2 horizon which lies below a conspicuous change of the external geomorphology of the platform. Backstepping of the platform margin by 12 km is observed in both platforms. Quantitative seismic interpretation shows that the karst observed in M1 platform is approximately 70–100 m deep, and the dendritic features are around 1–2 km in length and approximately 500 m wide; whereas, in the Jintan platform the dendritic features observed are up to 5 km in length with several 1 km wide circular/sinkhole features. More than 20 dendritic features orientated SE and NS were mapped mainly in the transitional area as well as the center of both platforms. The nature of the karst morphology in Central Luconia remains controversial; however, it is proposed to be of mixing zone karst origin.

Seismic Interpretation and Inversion Leading to an Accurate Reservoir Characterization in a Carbonate Environment

Seismic data acquired in the field show the subsurface reflectors or horizon among the geological strata, while the seismic inversion converts this reflector information into the acoustic impedance section which shows the layer properties based on lithology. The research aims to predict the porosity to identify the reservoir which is in between the tight layer. So, the output of the seismic inversion is much more batter than the seismic as it is closer to reality such as geology. Seismic inversion is frequently used to determine rock physics properties, for example, acoustic impedance and porosity.

Meso-Cenozoic negative inversion model for the Linhe Depression of Hetao Basin, China

The Linhe Depression is the largest tectonic unit in the Hetao Basin. The recently discovered commercial oil flow in the structural trap of wells JH2X and S5 has proved that the Meso-Cenozoic strata in the Linhe Depression have great exploration potential. Research on the kinematic model for the Mesozoic–Cenozoic Linhe Depression is important for analysing the geological conditions of hydrocarbon accumulation. In this study, field observations, seismic interpretation and scaled analogue modelling are performed. The results prove that the Linhe Depression experienced different stages of tectonic evolution, such as compressional depression (K1l), conversion from contraction to uniform subsidence (K1g), extensional rifting (E2–N2) and strike-slip deformation (Q), during the Mesozoic–Cenozoic eras. The kinematic model of negative inverted basins was first established with the early differential compression superimposed by the late extension. The seismic interpretation and analogue modelling results show that Jilantai Sag in the southern part of the Linhe Depression was subjected to compression from the Bayanwulashan fold–thrust belt on the NW side and the Helanshan fold–thrust belt on the SE side during Early Cretaceous time. Meanwhile, the Hanghou Sag in the northern part of the Linhe Depression was only compressed by the Langshan fold–thrust belt from the NW direction. The rifted structure generated by the extension from the SE direction during the Cenozoic Era resulted in the negative inversion of the pre-existing thrusts in different patterns. The intensity of negative inversion is controlled by several key factors, such as dip angle and the patterns of thrust faults, along with different basement textures. The morphological changes in the forebulge zone developed during Early Cretaceous time are responsible for the development of the segmented Central fault zones in the Hanghou Sag.

Impact of mechanical stratification on the structural style of the Lublin Basin, SE Poland: results of seismic interpretation and implications for quantification of deformation within the frontal parts of thin-skinned fold-and-thrust belts

We demonstrate how lithological and mechanical stratification of Ediacaran–Carboniferous sedimentary package governs strain partitioning in the Lublin Basin (LB) which was incorporated in the marginal portion of the Variscan fold-and-thrust belt. Based on the geometry of seismic reflectors, the pre-Permian–Mesozoic sedimentary sequence was subdivided into two structural complexes differing in structural style. The lower one reveals forelandward-vergent imbrication, while the upper one comprises fold train, second-order deformations, and multiple local detachments. Lithological composition of the upper structural complex controlled geometry, kinematics, and position of compressional deformations in stratigraphic profile. System of foreland-vergent thrusts which links lower and upper detachment developed due to efficiency of simple shear operating in heterogeneous clastic-carbonate-evaporitic strata of the Lower–Upper Devonian age. Internal homogeneity promoted the formation of conjugate sets of thrusts in Silurian shales and Upper Devonian limestones. Structural seismic interpretation combined with sequential restoration revealed localised thickening of Devonian strata and up to 5% difference in length of Devonian horizons. This mismatch is interpreted as a manifestation of distributed shortening, including layer-parallel shortening (LPS), which operated before or synchronously to the initiation of folding. The amount of distributed strain is comparable with numbers obtained in external parts of other fold-and-thrust belts. The outcomes derived from this study may act as a benchmark for studying variability in a structural style of multilayered sequences which were incorporated in the external portion of other fold-and-thrust belts.

Hydrocarbon Reservoir Characterization of ‘Khume’ Field, Offshore Niger Delta, Nigeria

The integrative approach of well log correlation and seismic interpretation was adopted in this study to adequately characterize and evaluate the hydrocarbon potentials of Khume field, offshore Niger Delta, Nigeria. 3-D seismic data and well logs data from ten (10) wells were utilized to delineate the geometry of the reservoirs in Khume field, and as well as to estimate the hydrocarbon reserves. Three hydrocarbon-bearing reservoirs of interest (D-04, D-06, and E-09A) were delineated using an array of gamma-ray logs, resistivity log, and neutron/density log suites. Stratigraphic interpretation of the lithologies in Khume field showed considerable uniform gross thickness across all three sand bodies. Results of petrophysical evaluations conducted on the three reservoirs correlated across the field showed that; shale volume ranged from 7-14%, total and effective porosity ranged from 19-26% and 17-23% respectively, NTG from 42 to 100%, water saturation from 40%-100% and permeability from 1265-2102 mD. Seismic interpretation established the presence of both synthetic and antithetic faults. A total of six synthetic and four antithetic faults were interpreted from the study area. Horizons interpretation was done both in the strike and dip directions. Time and depth structure maps revealed reservoir closures to be anticlinal and fault supported in the field. Hydrocarbon volumes were calculated using the deterministic (map-based) approach. Stock tank oil initially in place (STOIIP) for the proven oil column estimated for the D-04 reservoir was 11.13 MMSTB, 0.54 MMSTB for D-06, and 2.16 MMSTB for E-09A reservoir. For the possible oil reserves, a STOIIP value of 7.28 MMSTB was estimated for D-06 and 6.30 MMSTB for E-09A reservoir, while a hydrocarbon initially in place (HIIP) of 4.13 MMSTB of oil equivalents was derived for the undefined fluid (oil/gas) in D-06 reservoir. A proven gas reserve of 1.07 MMSCF was derived for the D-06 reservoir. This study demonstrated the effectiveness of 3-D seismic and well logs data in delineating reservoir structural architecture and in estimating hydrocarbon volumes

The geology of Pegasus Basin based on outcrop correlatives in southern Wairarapa and northeastern Marlborough, New Zealand

<p>Acquisition of high quality 2D seismic data by the New Zealand Government in 2009-10 (the PEG09 Survey) sparked new interest in Pegasus Basin, an offshore frontier basin situated east of central New Zealand. Although no wells have been drilled in Pegasus Basin, strata exposed onshore in southern Wairarapa and northeastern Marlborough provide useful analogues for the sedimentary fill of the basin. Using field observations in combination with petrographic analysis and seismic interpretation, this study provides a more complete understanding of the geology of Pegasus Basin. 13 outcrop localities are described from the surrounding southern Wairarapa and northern Marlborough regions, which are inferred to have been deposited in a range of depositional environments including fluvial, terrestrial and shallow marine deposits, through to inner – mid shelf, and deep marine channel-levee and submarine fans, with fine-grained sedimentation at bathyal depths. These outcrops provide representative and well-exposed examples of facies and lithologies typical of the depositional environments that are likely to exist in Pegasus Basin. Petrographic analysis of six Cretaceous and six Neogene sandstones from Marlborough and Wairarapa regions has revealed that they are compositionally classified as litharenites and feldspathic litharenites, derived from the Torlesse Supergroup. Primary porosity is best preserved in Neogene sandstones, whilst Cretaceous sandstones only tend to preserve secondary porosity, in the form of fractures or dissolution of framework grains. Carbonate cementation, compaction and authigenic clay formation are the biggest contributing factors that degrade reservoir quality. Seismic interpretation of the PEG09 survey has revealed that Pegasus Basin contains a sedimentary succession over 10,000 m thick, that mantles Early Cretaceous syn-tectonic strata in various states of deformation attained during mid-Cretaceous subduction at the eastern Gondwana margin. Key horizons mapped extensively over the basin highlight seismic reflection packages, which are linked to described outcrop localities onshore, based on reflection characteristics and geometries. The Miocene succession contains up to 4,000 m of sediments that are likely to include promising reservoir lithologies akin to the Great Marlborough Conglomerate of Marlborough, or the Whakataki Formation of Wairarapa.</p>