Optimization and Field Application of CO2 Gas Fracturing Technique for Enhancing CBM Extraction

Since most coalfields in China are commonly characterized by high gas content and low permeability, there is an urgent need to improve coal seam permeability and further enhance coal bed methane (CBM) extraction efficiency. As an emerging fracturing technology, the CO₂ gas fracturing (CGF) technology has been widely used because of its advantages of low cost, environmental protection and high fragmentation efficiency. In order to improve the fracturing ability of CGF technique and optimize the release orifices of discharge head, computational fluid dynamics model was used in this paper to simulate the flow fields of dynamic pressure of gas jet released from the orifices with different structures and other geometrical parameters. The results show that the orifice structure has a great influence on the flow field of gas jet, but little influence on the magnitude of the dynamic pressure. Besides, the maximum dynamic pressure of gas jet linearly decreases with the increase in the number of release orifices. Based on a series of simulation results, the discharge head which has single group of orifices with structure c, diameter of 24 mm can be identified as the best choice for fieldwork. Then, two field experiments were conducted in Pingdingshan and Changping coal mines to evaluate the enhanced CBM extraction efficiency by CGF. The results indicate that the CGF can effectively create a large number of cracks in a large range around the fracturing borehole in the coal seam and further significantly improve the permeability. And the CBM extraction efficiency can be improved to a higher level from a lower level and maintained for a long time. Besides, the effective influence radii caused by CGF in Pingdingshan and Changping coal mines are 15.19 m and 12.5 m, respectively. Compared with other fracturing techniques, the CGF technique has a promising application prospect.

     

Theory and Application of Pseudo-Reservoir Hydraulic Stimulation for Coalbed Methane Indirect Extraction in Horizontal Well: Part 1—Theory

Pseudo-reservoir stimulation in horizontal well is an effective technique for indirectly extracting coalbed methane (CBM) in soft coal from the surrounding rocks (pseudo-reservoir). However, systematic studies of the theory and on-site application of this technique are still lacking, which severely hinders its application. In this paper, the technical principles of pseudo-reservoir stimulation are analyzed firstly, and then, the technical advantages are demonstrated by experimental tests and theoretical analysis. The results show that the pseudo-reservoir generally possesses considerable gas adsorption capacity, with the gas content of 1.56–4.22 cm³/g (avg. 2.51 cm³/g) in Well XC-01, which can be extracted as supplementary resources. The fracability of the pseudo-reservoirs is 0.73–0.92, which is much higher than that of the coal seam, i.e., 0.03–0.43. Meanwhile, the compressive and tensile strength and cohesion of the pseudo-reservoir are higher than those of the coal seam, indicating pseudo-reservoir stimulation is more conducive to forming fracture network, and maintaining wellbore stability and fracture conductivity. The technical feasibility of pseudo-reservoir stimulation is determined by the regional geological conditions, showing simple tectonic conditions and well-developed surrounding rocks with high fracability and mechanical strength but low permeability, water sensitivity and water content are beneficial for the technique application. Note that the fracture conductivity in pseudo-reservoir is more stable and higher than that in coal seam, pseudo-reservoir stimulation is beneficial for the CBM extraction from both hard and soft coal seams. By minimizing the gas diffusion distance, this technique overcomes the technical obstacles to the CBM commercialized production in soft coal.

     

Gas Flow Characteristics and Optimization of Gas Drainage Borehole Layout in Protective Coal Seam Mining: A Case Study from the Shaqu Coal Mine,Shanxi Province,China

With increasing demands for coal resources, coal has been gradually mined in deep coal seams. Due to high gas content, pressure and in situ stress, deep coal seams show great risks of coal and gas outburst. Protective coal seam mining, as a safe and effective method for gas control, has been widely used in major coal-producing countries in the world. However, at present, the relevant problems, such as gas seepage characteristics and optimization of gas drainage borehole layout in protective coal seam mining have been rarely studied. Firstly, by combining with formulas for measuring and testing permeability of coal and rock mass in different stress regimes and failure modes in the laboratory, this study investigated stress–seepage coupling laws by using built-in language Fish of numerical simulation software FLAC^3D. In addition, this research analyzed distribution characteristics of permeability in a protected coal seam in the process of protective coal seam mining. Secondly, the protected coal seam was divided into a zone with initial permeability, a zone with decreasing permeability, and permeability increasing zones 1 and 2 according to the changes of permeability. In these zones, permeability rises the most in the permeability increasing zone 2. Moreover, by taking Shaqu Coal Mine, Shanxi Province, China as an example, layout of gas drainage boreholes in the protected coal seam was optimized based on the above permeability-based zoning. Finally, numerical simulation and field application showed that gas drainage volume and concentration rise significantly after optimizing borehole layout. Therefore, when gas is drained through boreholes crossing coal seams during the protective coal seam mining in other coal mines, optimization of borehole layout in Shaqu Coal Mine has certain reference values.

     

Structural controls on non fabric‐selective dolomitization within rift‐related basin‐bounding normal fault systems: Insights from the Hammam Faraun Fault,Gulf of Suez,Egypt

Fault‐controlled dolostone bodies have been described as potential hydrocarbon‐bearing reservoirs. Numerous case studies have described the shape and size of these often non fabric selective dolostone bodies within the vicinity of crustal‐scale lineaments, usually from Palaeozoic or Mesozoic carbonate platforms, which have undergone one or more phases of burial and exhumation. There has been little attention paid, however, to fault‐strike variability in dolostone distribution or the preferential localization of these bodies on particular faults. This study focuses on dolostone bodies adjacent to the Hammam Faraun Fault (HFF), Gulf of Suez. This crustal‐scale normal fault was activated in the Late Oligocene, coincident with the onset of extension within the Suez Rift. Dolomitization in the prerift Eocene Thebes Formation occurred in the immediate footwall of the HFF forming two massive, non facies selective dolostone bodies, ca. 500 m wide. Facies‐controlled tongues of dolostone on the margins of the massive dolostone bodies extend for up to 100 m. The geochemical signature of the dolostone bodies is consistent with replacement by Miocene seawater, contemporaneous with the rift climax and localization of strain along the HFF. A conceptual model of dolomitization from seawater that circulated within the HFF during the rift climax is presented. Seawater was either directly drawn down the HFF or circulated from the hanging wall basin via a permeable aquifer towards the HFF. The lateral extent of the massive dolostone bodies was controlled by pre‐existing HFF‐parallel fracture corridors on the outer margins of the damage zone of the fault. The behaviour of these fracture corridors alternated between acting as barriers to fluid flow before rupture and acting as flow conduits during or after rupture. Multiple phases of dolomitization and recrystallization during the ca. 10 Ma period in which dolomitization occurred led to mottled petrographical textures and wide‐ranging isotopic signatures. The localization of dolomitization on the HFF is interpreted to reflect its proximity to a rift accommodation zone which facilitated vertical fluid flow due to perturbed and enhanced stresses during fault interaction. It is possible that the presence of jogs along the strike of the fault further focused fluid flux. As such, it is suggested that the massive dolostones described in this study provide a window into the earliest stages of formation of fault‐controlled hydrothermal dolostone bodies, which could have occurred in other areas and subsequently been overprinted by more complex diagenetic and structural fabrics.     

Characteristics of Permeability Changes in Bituminous Coal Under Conditions of Stress Variation Due to Repeated Mining Activities

The factors affecting permeability change under repeated mining of coal seams are important study aspects that need to be explored. This study combined various stress variation characteristics of protective seam mining and simplified the stress path of repeated mining in protective seam mines. Based on the results from the bespoke gas flow and displacement testing apparatus, seepage tests for simulated repetitive mining were carried out. The results simulated the actual behavior very well. With any drastic increase in the mining influence, the axial deviation stress in the stress path increased, and the greater the difference in coal permeability during the unloading and stress recovery stage, the more substantial the increase in permeability. The change in coal permeability was significantly influenced by the severity of simulated repeated mining cycles. When the mining stress exceeded a critical value, the permeability of the coal sample increased with the increase in the number of loading and unloading cycles, but the reverse was true when the mining stress was lower than the critical value. The effective sensitivity of seepage to the applied stress decreased with an increase in the number of stress cycles. With a decrease in the deviation stress, that is, with lower severity of mining influence, the effective sensitivity of coal seepage to stress gradually decreased.

     

Evaluation of Relative Permeability in Coalbed Methane Reservoirs Based on Production Data: A Case Study in Qinshui Basin,China

Relative permeability is an important feature to characterize two-phase flow in coalbed methane (CBM) reservoirs, as it can be widely used in laboratory, simulation studies and field production. The main methods to derive relative permeability curves include history match, laboratory core test and production data. In China, most of the acquired CBM well data are the field production data, so this study intended to evaluate of CBM relative permeability based on production data. The Zhengzhuang area in Qinshui Basin was chosen as a case study. Since flow equations can only be used in radial flow, flow regime was first identified for radial flow. Then, the Palmer et al. (in: International coalbed methane symposium, Tuscaloosa, 2007) absolute permeability model was used to characterize absolute permeability, so that the effects of relative permeability and absolute permeability changes can be isolated. Material balance equation (MBE) was also applied to derive water saturation. Therefore, the relative permeability curve can be derived by combination of flow equations, Palmer et al. (2007) absolute permeability model and MBE based on real field production data. In addition, relative permeability curves of producing wells from different zones of the Zhengzhuang area were compared and the possible reason for the difference was also discussed. The work presented here can provide a useful and practical instruction for the derivation of relative permeability of China’s CBM wells.

     

Dual-Porosity Coupled Borehole Gas Flow Model: A New Method for Inversion of Coal Seam Permeability

The permeability of a coal seam is an important index for coal mine gas control and coalbed methane development, and its magnitude determines the degree of difficulty of gas drainage. To obtain the permeability value, a dimensionless mathematical model for dual-porosity borehole gas-coupled flow in a coal seam was established and adopted using a simulator developed by our group. A new method of inversion was developed to determine the fracture permeability coefficient λ_f and the matrix micro-channel diffusion coefficient K_m by fitting the simulated results with onsite measured data. A range of simulations quantified the effects of different dimensionless parameters on gas migration. The results verified the feasibility of the inversion method based on the high matching degree of the fitted results, and the dimensionless mathematical model was accurate. The desorption and release of adsorbed gas from the center to the surface in coal matrices were heterogeneous, and unsteady states and gas migration times in coal matrices cannot be neglected. The new method can be introduced to analyze the problem of gas migration in different coal reservoirs, simplify the corresponding calculation and computational processes, and provide guidance in determining the permeability of coal seams.

     

沙埋对小麦(Triticum aestivum)生长的影响及其生理响应

为了解沙埋对小麦(Triticum aestivum)生长的影响及其生理响应,2010年在科尔沁沙地研究了不同沙埋深度下小麦的存活率、株高、地上地下生物量、籽实产量、丙二醛(MDA)含量、膜透性、保护酶(超氧化物歧化酶,SOD;过氧化物酶,POD;过氧化氢酶,CAT)活性和渗透调节物质含量变化。结果表明:随着沙埋深度的增加,小麦存活率、株高、地上地下生物量和籽实产量均显著下降,完全沙埋下第6天以后植株全部死亡。沙埋第6天,随着沙埋深度的增加,MDA含量、CAT活性、可溶性糖含量下降,POD活性变化不明显,但膜透性、SOD活性和脯氨酸含量显著增加。沙埋第12天,随着沙埋厚度增加,MDA含量和膜透性,SOD、POD和CAT活性,脯氨酸和可溶性糖含量均显著增加。沙埋导致小麦死亡率增加、株高及生物产量下降的主要原因不是水分胁迫,沙埋导致的光合面积降低、黑暗和无氧呼吸可能是其死亡和生长受到抑制的主要外部因素,而膜脂过氧化导致的膜透性增加可能是其死亡或生长受到抑制的主要生理机制。保护酶活性增强和渗透调节物质含量增加,对于减轻其细胞膜受损和防止细胞质渗漏起到了重要作用。     

Present‐day stress orientation in the Clarence‐Moreton Basin of New South Wales,Australia: a new high density dataset reveals local stress rotations

Early phases of the Australian Stress Map project revealed that plate boundary forces acting on the Indo‐Australian Plate control the long wavelength of the maximum horizontal present‐day stress orientation in the Australian continent. However, all numerical models of the stress field to date are unable to predict the observed orientation of maximum horizontal stress in the northeast of New South Wales, Australia. Recent coal seam gas exploration in the Clarence‐Moreton Basin, eastern Australia, provides an opportunity to better evaluate the state of crustal stress in this part of the continent where only limited information was available prior to this study. Herein, we conduct the first analysis of the present‐day tectonic stress in the Clarence‐Moreton Basin, from drilling‐induced tensile fractures and borehole breakouts interpreted using 11.3 km of acoustic image logs in 27 vertical wells. A total of 2822 drilling‐induced stress indicators suggest a mean orientation of N069°E (±23°) for the maximum horizontal present‐day stress in the basin which is different from that predicted by published geomechanical‐numerical models. In addition, we find significant localised perturbations of borehole breakouts, both spatially and with depth, that are consistent with stress variations near faults, fractures and lithological contrasts, indicating that local structures are an important source of stress in the basin. The observation that structures can have a major control on the stresses in the basin suggests that, while gravity and plate boundary forces have the major role in the long wavelength (first‐order) stress pattern of the continent, local perturbations are significant and can lead to substantial changes in the orientation of the maximum horizontal present‐day stress, particularly at the basin scale. These local perturbations of stress as a result of faults and fractures have important implications in borehole stability and permeability of coal seam gas reservoirs for safe and sustainable extraction of methane in this area.     

Effects of sand burial on survival and growth of Artemisia halodendron and its physiological response

There is a great deal of literature on the effects of sand burial upon the survival and growth of desert plants, but the physiological adaption mechanisms of desert plants to sand burial have as yet ra...     

Origin of early overpressure in the Upper Devonian Catskill Delta Complex, western New York state

The Upper Devonian Rhinestreet black shale of the western New York state region of the Appalachian Basin has experienced multiple episodes of overpressure generation manifested by at least two sets of natural hydraulic fractures. These overpressure events were thermal in origin and induced by the generation of hydrocarbons during the Alleghanian orogeny close to or at the Rhinestreet's ～3.1 km maximum burial depth. Analysis of differential gravitational compaction strain of the organic‐rich shale around embedded carbonate concretions that formed within a metre or so of the seafloor indicates that the Rhinestreet shale was compacted ～58%. Compaction strain was recalculated to a palaeoporosity of 37.8%, in excess of that expected for burial >3 km. The palaeoporosity of the Rhinestreet shale suggests that porosity reduction caused by normal gravitational compaction of the low‐permeability carbonaceous sediment was arrested at some depth shy of its maximum burial depth by pore pressure in excess of hydrostatic. The depth at which the Rhinestreet shale became overpressured, the palaeo‐fluid retention depth, was estimated by use of published normal compaction curves and empirical porosity‐depth algorithms to fall between 850 and 1380 m. Early and relatively shallow overpressuring of the Rhinestreet shale likely originated by disequilibrium compaction induced by a marked increase in sedimentation rate in the latter half of the Famennian stage (Late Devonian) as the Catskill Delta Complex prograded westward across the Appalachian Basin in response to Acadian tectonics. The regional Upper Devonian stratigraphy of western New York state indicates that the onset of overpressure occurred at a depth of ～1100 m, well in advance of the Rhinestreet shale's entry into the oil window during the Alleghanian orogeny.     

Tectono‐sedimentary evolution of the Plio‐Pleistocene Corinth rift,Greece

The onshore central Corinth rift contains a syn‐rift succession >3 km thick deposited in 5–15 km‐wide tilt blocks, all now inactive, uplifted and deeply incised. This part of the rift records upward deepening from fluviatile to lake‐margin conditions and finally to sub‐lacustrine turbidite channel and lobe complexes, and deep‐water lacustrine conditions (Lake Corinth) were established over most of the rift by 3.6 Ma. This succession represents the first of two phases of rift development – Rift 1 from 5.0–3.6 to 2.2–1.8 Ma and Rift 2 from 2.2–1.8 Ma to present. Rift 1 developed as a 30 km‐wide zone of distributed normal faulting. The lake was fed by four major N‐ to NE‐flowing antecedent drainages along the southern rift flank. These sourced an axial fluvial system, Gilbert fan deltas and deep lacustrine turbidite channel and lobe complexes. The onset of Rift 2 and abandonment of Rift 1 involved a 30 km northward shift in the locus of rifting. In the west, giant Gilbert deltas built into a deepening lake depocentre in the hanging wall of the newly developing southern border fault system. Footwall and regional uplift progressively destroyed Lake Corinth in the central and eastern parts of the rift, producing a staircase of deltaic and, following drainage reversal, shallow marine terraces descending from >1000 m to present‐day sea level. The growth, linkage and death of normal faults during the two phases of rifting are interpreted to reflect self‐organization and strain localization along co‐linear border faults. In the west, interaction with the Patras rift occurred along the major Patras dextral strike‐slip fault. This led to enhanced migration of fault activity, uplift and incision of some early Rift 2 fan deltas, and opening of the Rion Straits at ca. 400–600 ka. The landscape and stratigraphic evolution of the rift was strongly influenced by regional palaeotopographic variations and local antecedent drainage, both inherited from the Hellenide fold and thrust belt.     

Tectonic uplift of the Xichang Basin (SE Tibetan Plateau) revealed by structural geology and thermochronology data

The Xichang Basin in southeastern Tibet provides crucial information about formation and tectonic processes affecting the eastern Tibetan Plateau. To determine when and how the uplift developed, we conducted detailed studies of structures and obtained thermochronology data from the Xichang Basin and its periphery. The Xichang Basin is characterized by gentle deformation of the strata, segmented by an E‐vergent boundary thrust fault. Two stages of deformation, strike‐slip followed by an E‐W oriented shortening resulted in oblique shortening between the southeastern Tibetan Plateau and the Sichuan Basin. New apatite fission‐track data interpreted together with (U‐Th)/He data confirm a simple burial/heating and exhumation/cooling history across the Xichang Basin and its periphery. Subsidence and burial of the Xichang Basin peaked between 80–30 Ma, followed by mountain building with a protracted cooling starting at around 40–20 Ma, with rates of ca. 2.0–8.0 °C Myr⁻¹ (i.e. 0.1–0.3 mm year⁻¹). Our data indicate that the Xichang Basin has experienced ca. 2.5–5 km of exhumation, much more intensive than the ca. 1–2 km of exhumation inferred for the southwestern Sichuan Basin. Restored balanced cross‐sections of post‐Late‐Triassic strata along a ca. 250 km traverse indicate ca. 10–20% east‐west shortening strain (i.e. ca. 20–30 km) at the southeastern Tibetan Plateau during Cenozoic time. Study of crustal thickening and erosion supports a tectonic shortening mechanism to account for the uplift of the Xichang Basin on the southeastern Tibetan Plateau.     

Cenozoic tectonic subsidence in the Qiongdongnan Basin,northern South China Sea

A number of major controversies exist in the South China Sea, including the timing and pattern of seafloor spreading, the anomalous alternating strike‐slip movement on the Red River Fault, the existence of anomalous post‐rift subsidence and how major submarine canyons have developed. The Qiongdongnan Basin is located in the intersection of the northern South China Sea margin and the strike‐slip Red River fault zone. Analysing the subsidence of the Qiongdongnan Basin is critical in understanding these controversies. The basin‐wide unloaded tectonic subsidence is computed through 1D backstripping constrained by the reconstruction of palaeo‐water depths and the interpretation of dense seismic profiles and wells. Results show that discrete subsidence sags began to form in the central depression during the middle and late Eocene (45–31.5 Ma). Subsequently in the Oligocene (31.5–23 Ma), more faults with intense activity formed, leading to rapid extension with high subsidence (40–90 m Myr⁻¹). This extension is also inferred to be affected by the sinistral movement of the offshore Red River Fault as new subsidence sags progressively formed adjacent to this structure. Evidence from faults, subsidence, magmatic intrusions and strata erosion suggests that the breakup unconformity formed at ca. 23 Ma, coeval with the initial seafloor spreading in the southwestern subbasin of the South China Sea, demonstrating that the breakup unconformity in the Qiongdongnan Basin is younger than that observed in the Pearl River Mouth Basin (ca. 32–28 Ma) and Taiwan region (ca. 39–33 Ma), which implies that the seafloor spreading in the South China Sea began diachronously from east to west. The post‐rift subsidence was extremely slow during the early and middle Miocene (16 m Myr⁻¹, 23–11.6 Ma), probably caused by the transient dynamic support induced by mantle convection during seafloor spreading. Subsequently, rapid post‐rift subsidence occurred during the late Miocene (144 m Myr⁻¹, 11.6–5.5 Ma) possibly as the dynamic support disappeared. The post‐rift subsidence slowed again from the Pliocene to the Quaternary (24 m Myr⁻¹, 5.5–0 Ma), but a subsidence centre formed in the west with the maximum subsidence of ca. 450 m, which coincided with a basin with the sediment thickness exceeding 5500 m and is inferred to be caused by sediment‐induced ductile crust flow. Anomalous post‐rift subsidence in the Qiongdongnan Basin increased from ca. 300 m in the northwest to ca. 1200 m in the southeast, and the post‐rift vertical movement of the basement was probably the most important factor to facilitate the development of the central submarine canyon.     

中国陆上天然气资源的经济效用影响因素研究(英文)

本文研究了中国陆上天然气经济效用的地质及相关影响因素。主要研究结论如下:天然气勘探开发成本主要与气田(藏)的深度及储盖层的岩性参数相关,开采成本主要受自然地理因素以及相应储层物性参数影响,而气田(藏)丰度、有效厚度、孔隙度、渗透率和气藏类型是影响天然气产量的主要因素。基于上述研究结论,建立了针对投资成本、价格因素和气田经济价值的千米井深日产量计算公式和区域判断标准。根据判别标准,本文分析了中国不同区域且具有指标意义的天然气田(藏)的经济效用,并针对中国天然气产业经济发展提出了相应的结论和建议。     

Nano-mechanical Properties and Pore-Scale Characterization of Different Rank Coals

Characterization of coal micro-structure and the associated rock mechanical properties are of key importance for coal seam exploration, coal bed methane development, enhanced coal bed methane production and CO₂ storage in deep coal seams. Considerable knowledge exists about coal chemical properties, but less is known about the nanoscale to the micro-scale structure of coals and how they change with coal strength across coal ranks. Thus, in this study, 3D X-ray micro-computed tomography (with a voxel size of 3.43 µm) and nano-indentation tests were conducted on coal samples of different ranks from peat to anthracite. The micro-structure of peats showed a well-developed pore system with meso- and micro-pores. The meso-pores essentially disappear with increasing rank, whereas the micro-pores persist and then increase past the bituminous rank. The micro-fracture system develops past the peat stage and by sub-bituminous ranks and changes into larger and mature fracture systems at higher ranks. The nano-indentation modulus showed the increasing trend from low- to high-rank coal with a perfect linear relationship with vitrinite reflectance and is highly correlated with carbon content as expected.

     

Spatial distribution of micrometre‐scale porosity and permeability across the damage zone of a reverse‐reactivated normal fault in a tight sandstone: Insights from the Otway Basin,SE Australia

Knowledge of the permeability structure of fault‐bearing reservoir rocks is fundamental for developing robust hydrocarbon exploration and fluid monitoring strategies. Studies often describe the permeability structure of low porosity host rocks that have experienced simple tectonic histories, while investigations of the influence of faults with multiple‐slip histories on the permeability structure of porous clastic rocks are limited. We present results from an integrated petrophysical, microstructural, and mineralogical investigation of the Eumeralla Formation (a tight volcanogenic sandstone) within the hanging wall of the Castle Cove Fault which strikes 30 km NE–SW in the Otway Basin, southeast Australia. This late Jurassic to Cenozoic‐age basin has experienced multiple phases of extension and compression. Core plugs and thin sections oriented relative to the fault plane were sampled from the hanging wall at distances of up to 225 m from the Castle Cove Fault plane. As the fault plane is approached, connected porosities increase by ca. 10% (17% at 225 m to 24% at 0.5 m) and permeabilities increase by two orders of magnitude (from 0.04 mD at 225 m to 1.26 mD at 0.5 m). Backscattered Scanning Electron Microscope analysis shows that microstructural changes due to faulting have enhanced the micrometre‐scale permeability structure of the Eumeralla Formation. These microstructural changes have been attributed to the formation of microfractures and destruction of original pore‐lining chlorite morphology as a result of fault deformation. Complex deformation, that is, formation of macrofractures, variably oriented microfractures, and a hanging wall anticline, associated with normal faulting and subsequent reverse faulting, has significantly influenced the off‐fault fluid flow properties of the protolith. However, despite enhancement of the host rock permeability structure, the Eumeralla Formation at Castle Cove is still considered a tight sandstone. Our study shows that high‐resolution integrated analyses of the host rock are critical for describing the micrometre‐scale permeability structure of reservoir rocks with high porosities, low permeabilities, and abundant clays that have experienced complex deformation.     

Normal fault evolution and coupled landscape response: examples from the Southern Apennines,Italy

We present new data addressing the evolution, activity and geomorphic impact of three normal faults in the Southern Apennines: the Vallo di Diano, East Agri and Monti della Maddalena faults. We show that these faults have minimum total throws of ca. 1000–2000 m, and throw rates of ca. 0.7–1 mm year⁻¹ for at least the last ca. 18 ka. We demonstrate that for the Vallo di Diano and East Agri faults, the landscape is effectively recording tectonics, with relief, channel and catchment slopes varying along fault strike in the same manner as normal fault activity does, with little apparent influence of lithology. We therefore use these data to reconstruct the time‐integrated history of fault interaction and growth. From the distribution of knickpoints on the footwall channels, we infer two episodes of base level change, which we attribute to fault interaction episodes. We reconstruct the amount of throw accumulated after each of these events, and the segments involved in each, from the fault throw profiles, and use fault interaction theory to estimate the magnitude of the perturbations and past throw rates. We estimate that fault linkage events took place 0.7 ± 0.2 Ma and 1.4 ± 0.3 Ma in the Vallo di Diano fault, and 1 ± 0.1 in the East Agri Fault, and that both faults likely started their activity between 3 and 3.5 Ma. These fault linkage scenarios are consistent with the observed knickpoint heights. This method for reconstructing fault evolution could potentially be applied for any normal faults for which there is information about throw and throw rates, and in which channels are transiently responding to tectonics.     

Basin tectonic history and paleo‐physiography of the pelagian platform,northern Tunisia,using vitrinite reflectance data

Constraining the thermal, burial and uplift/exhumation history of sedimentary basins is crucial in the understanding of upper crustal strain evolution and also has implications for understanding the nature and timing of hydrocarbon maturation and migration. In this study, we use Vitrinite Reflectance (VR) data to elucidate the paleo‐physiography and thermal history of an inverted basin in the foreland of the Atlasic orogeny in Northern Tunisia. In doing so, it is the primary aim of this study to demonstrate how VR techniques may be applied to unravel basin subsidence/uplift history of structural domains and provide valuable insights into the kinematic evolution of sedimentary basins. VR measurements of both the onshore Pelagian Platform and the Tunisian Furrow in Northern Tunisia are used to impose constraints on the deformation history of a long‐lived structural feature in the studied region, namely the Zaghouan Fault. Previous work has shown that this fault was active as an extensional structure in Lower Jurassic to Aptian times, before subsequently being inverted during the Late Cretaceous Eocene Atlas I tectonic event and Upper Miocene Atlas II tectonic event. Quantifying and constraining this latter inversion stage, and shedding light on the roles of structural inheritance and the basin thermal history, are secondary aims of this study. The results of this study show that the Atlas II WNW‐ESE compressive event deformed both the Pelagian Platform and the Tunisian Furrow during Tortonian‐Messinian times. Maximum burial depth for the Pelagian Platform was reached during the Middle to Upper Miocene, i.e. prior to the Atlas II folding event. VR measurements indicate that the Cretaceous to Ypresian section of the Pelagian Platform was buried to a maximum burial depth of ~3 km, using a geothermal gradient of 30°C/km. Cretaceous rock samples VR values show that the hanging wall of the Zaghouan Fault was buried to a maximum depth of <2 km. This suggests that a vertical km‐scale throw along the Zaghouan Fault pre‐dated the Atlas II shortening, and also proves that the fault controlled the subsidence of the Pelagian Platform during the Oligo‐Miocene. Mean exhumation rates of the Pelagian Platform throughout the Messinian to Quaternary were in the order of 0.3 mm/year. However, when the additional effect of Tortonian‐Messinian folding is accounted for, exhumation rates could have reached 0.6–0.7 mm/year.