Chitosan-Alginate Sponge: Preparation and Application in Curcumin Delivery for Dermal Wound Healing in Rat

A biodegradable sponge, composed of chitosan (CS) and sodium alginate (SA), was successfully obtained in this work. The sponge was ethereal and pliable. The chemical structure and morphology of the sponges was characterized by FTIR and SEM. The swelling ability, in vitro drug release and degradation behaviors, and an in vivo animal test were employed to confirm the applicability of this sponge as a wound dressing material. As the chitosan content in the sponge decreased, the swelling ability decreased. All types of the sponges exhibited biodegradable properties. The release of curcumin from the sponges could be controlled by the crosslinking degree. Curcumin could be released from the sponges in an extended period for up to 20 days. An in vivo animal test using SD rat showed that sponge had better effect than cotton gauze, and adding curcumin into the sponge enhanced the therapeutic healing effect

Gas-Bearing Property in Deep Marine Shale and Its Micro Controlling Factors: Evidence from the Lower Silurian Longmaxi Formation in Southern Sichuan, China

AbstractThe gas content in shale reservoirs is often determined by the micro storage and sealing capacities of the reservoir. Deep shale reservoirs are in the high- or over-thermale maturity stage and have complex pore structure and connectivity, which are highly heterogeneous in vertical distribution. Research on the gas-bearing property of deep shale reservoirs is limited by these complex microscopic conditions. To analyze the gas-bearing characteristics of deep shale reservoirs, this work collected and summarized data on total organic carbon content, mineral composition, porosity, water saturation, and gas content measured on-site for the Longmaxi Formation in the Sichuan Basin in southern Sichuan, China. Then, experimental methods, such as X-ray photoelectron spectroscopy, transmission electron microscope, low-pressure N2 adsorption, spontaneous imbibition, and high-pressure methane adsorption, were used to analyze the micro storage and sealing capacities of the deep shale reservoirs. The results show that, different from shallow shale reservoirs (<3500 m), deep shale reservoirs have a higher graphitization degree and water saturation. An abundance of graphite structures often leads to weak resistance of organic matter to compression, deformation, or even collapse of pores in organic matter and severe damage to the gas storage space. However, a higher degree of graphitization can enhance the ability of the shale reservoirs to adsorb gas and self-sealing. The high water saturation in the reservoirs can interact with clay minerals and negatively affect the gas accumulation, storage, and transmission capacities of the shale reservoirs. However, the upper shale reservoirs with higher water saturation can seal the lower shale reservoirs, helping it preserve shale gas. Based on the vertical distribution of graphite structure, clay minerals contents, lithofacies, and water content in deep shale reservoirs, the essential microscopic conditions for deep shale reservoirs to have high gas content were proposed. This paper provides a detailed explanation and evaluation of deep shale’s storage and sealing capacities at the microscopic scale and can serve as a reference for further identifying the patterns for high-yield and rich shale gas reservoirs and improving deep shale gas exploration technologies

Source-reservoir rock assemblages and hydrocarbon accumulation models in the Middle-Lower Jurassic of eastern Sichuan Basin, China

The eastern Sichuan Basin in China holds vast potential for oil and gas exploration in the Lower-Middle Jurassic strata. However, the geological characteristics and hydrocarbon accumulation patterns of this region remain largely unclear. During the deposition period of the Lower-Middle Jurassic strata, the eastern Sichuan is characterized by the formation of multiple sets of source, reservoir, and caprock assemblages through depositing lake-delta-fluvial deposits, which have great exploration potential. The Jurassic source rocks in eastern Sichuan are mainly developed in the Dongyuemiao Member, Da’anzhai Member, and Liangshan Formation. These source rocks have a total organic carbon (TOC) content greater than 1 and a varying range of organic matter maturity, with a Ro value of 0.8–2.0. The kerogen in these source rocks is primarily type II, with a smaller proportion being type III. A range of reservoir rocks can be found in the Jurassic strata of eastern Sichuan, with sandstone reservoirs being predominantly found in the Liangshan Formation, Shaximiao Formation, and Zhenzhuchong Member. Shale reservoirs are mostly present in the Dongyuemiao, Da’anzhai, Liangshan, and Maanshan Members, and there is a limited distribution of limestone reservoirs in the Da’anzhai Member and Dongyuemiao Formation. The arrangement of source rocks and reservoir rocks in eastern Sichuan has led to the formation of three types of reservoir-forming combinations, including lower generation and upper storage, self-generation and self-storage, and composite. Sandstone reservoirs are typically of lower generation and upper storage, shale reservoirs are primarily of self-generation and self-storage, and limestone reservoirs are mostly composite. The exploration of Jurassic oil and gas in eastern Sichuan should prioritize “layer and area selections.” The Da’anzhai, Dongyuemiao, and Liangshan shale reservoirs should be the primary exploration targets, with the semi-deep lake deposits in the syncline area being the most favorable. The degree of fracture development in the exploration area also has a significant impact on the shale oil and gas content. The Liangshan Formation and Shaximiao Formation sandstone reservoirs can serve as secondary exploration targets, with anticline areas that have better sealing conditions being more favorable. Limestone reservoirs have limited distribution, and exploration areas with high and steep fractures are relatively more advantageous

Gas-Bearing Property in Deep Marine Shale and Its Micro Controlling Factors: Evidence from the Lower Silurian Longmaxi Formation in Southern Sichuan, China

Abstract The gas content in shale reservoirs is often determined by the micro storage and sealing capacities of the reservoir. Deep shale reservoirs are in the high- or over-thermale maturity stage and have complex pore structure and connectivity, which are highly heterogeneous in vertical distribution. Research on the gas-bearing property of deep shale reservoirs is limited by these complex microscopic conditions. To analyze the gas-bearing characteristics of deep shale reservoirs, this work collected and summarized data on total organic carbon content, mineral composition, porosity, water saturation, and gas content measured on-site for the Longmaxi Formation in the Sichuan Basin in southern Sichuan, China. Then, experimental methods, such as X-ray photoelectron spectroscopy, transmission electron microscope, low-pressure N2 adsorption, spontaneous imbibition, and high-pressure methane adsorption, were used to analyze the micro storage and sealing capacities of the deep shale reservoirs. The results show that, different from shallow shale reservoirs (&amp;lt;3500 m), deep shale reservoirs have a higher graphitization degree and water saturation. An abundance of graphite structures often leads to weak resistance of organic matter to compression, deformation, or even collapse of pores in organic matter and severe damage to the gas storage space. However, a higher degree of graphitization can enhance the ability of the shale reservoirs to adsorb gas and self-sealing. The high water saturation in the reservoirs can interact with clay minerals and negatively affect the gas accumulation, storage, and transmission capacities of the shale reservoirs. However, the upper shale reservoirs with higher water saturation can seal the lower shale reservoirs, helping it preserve shale gas. Based on the vertical distribution of graphite structure, clay minerals contents, lithofacies, and water content in deep shale reservoirs, the essential microscopic conditions for deep shale reservoirs to have high gas content were proposed. This paper provides a detailed explanation and evaluation of deep shale’s storage and sealing capacities at the microscopic scale and can serve as a reference for further identifying the patterns for high-yield and rich shale gas reservoirs and improving deep shale gas exploration technologies.</jats:p

Genetic Types and Main Control Factors of Microfractures in Tight Oil Reservoirs of Jimsar Sag

Microfractures are key for migrating and aggregating hydrocarbon source rocks and fracturing oil-gas exploitation in tight reservoirs. In this study, rock samples from the Lucaogou Formation tight reservoirs in Xinjiang, China, were studied using multidisciplinary techniques to investigate the genetic types and main control factors of microfractures. Results indicated that the Lucaogou Formation mainly developed diagenetic microfractures followed by tectonic microfractures, with slight formations of granular microfractures. These observations were used to clarify the relationship between the development of microfractures and the pore fluid content, lithology, mineral composition, and stratum thickness. A higher pore fluid content corresponded to a lower compressive strength of the rocks and a larger ring count, resulting in a higher probability of failure and microfracture formation. Tight reservoirs containing more quartz and carbonate minerals were found to develop more microfractures. Quartz grains showed fractures at the margins under stress, which increased the pore permeability of rocks. Carbonate minerals tended to form microfractures owing to corrosion. Microfracture formation mechanisms differed depending on lithology, and microfractures were found to develop most in dolomite and dolomitic siltstones and least in mudstone. Muddy rocks developed fewer tectonic fractures because they can easily absorb stress and undergo plastic deformation. Within a certain stratum thickness range, the average single-well fracture space and stratum thickness showed positive correlations. Moreover, the fracture space increased and the fracture density decreased as the stratum thickness increased. When the stratum thickness was less than 2.5 m, the fracture space increased linearly with the stratum thickness, and when the stratum thickness was greater than 2.5 m, the fracture space remained constant. This study will provide an essential scientific basis for enhancing tight oil recovery.</jats:p

Reservoir quality prediction of deeply buried tight sandstones in extensively faulted region: A case from the middle-Upper Jurassic Shishugou Group in central Junggar Basin, NW China

The reservoir quality of tight sandstones is generally determined by the depositional environment, burial depth and diagenesis. However, the relationship between reservoir quality of tight sandstones and the controlling factors are very complicated. Deeply buried Middle-Upper Jurassic Shishugou Group sandstones are important tight oil sandstone reservoirs in the central Junggar Basin of NW china. The individual sandstones are thin (2–20m, av.7.8m), overlain by an unconformity and directly connected to the source rock by a well-developed fault system. The diagenetic system and reservoir quality of the Shishugou Group sandstones in the Central Junggar Basin was investigated using petrology, mineralogy, pore characteristics, sedimentary facies, burial and thermal history, knowledge of hydrocarbon charging, fault/fracture system, diagenetic reactions and sequence, controlling factors of reservoir quality, paleo-porosity reconstruction and formation mechanism of high-quality reservoir. The thin-section observation, scanning electron microscope (SEM and BSD), granularity analysis, Xray diffraction (XRD) and fluorescence microscope, 3D seismic and well logging analysis were used in this research. The top unconformity and faults system were the pathways for water and hydrocarbon migration. Organic acids and meteoric water with high concentrations of CO2 were the main fluids that caused dissolution of volcanic rock fragments, feldspar, analcime cement and early calcite cement. The paleo-porosity variation of Shishugou Group sandstones was analyzed quantitatively by the inversion and back stripping with the constrain of diagenetic evolution history and theoretical compaction models. The comprehensive researches including the origin of pore waters, origin of acidic fluids, fault/fracture system and hydrocarbon charging history, show that near-surface or meteoric diagenetic reactions of Shishugou Group sandstones closely beneath top unconformities were in open (geochemical) diagenetic systems, and that diagenetic (geochemical) systems were relatively open, especially in the faults-developed zone during burial process. The central sandstone body of the point bar, underwater distributary channel and distributary channel, which were cut through by the oil source fault, retained high-quality reservoir. The reservoir quality can be mostly predicted as a function of sedimentary environment (sedimentary facies and provenance), diagenetic reactions and burial history with the constrain of source rocks, diagenetic system and fault system

Diagenetic characteristics, evolution, controlling factors of diagenetic system and their impacts on reservoir quality in tight deltaic sandstones: Typical example from the Xujiahe Formation in Western Sichuan Foreland Basin, SW China

Deeply buried (3000–5000 m), deltaic sandstones of the Upper Triassic Xujiahe Formation are important tight gas reservoirs in the Sichuan Foreland Basin, China. The diagenesis of these tight sandstones was examined using a variety of petrographic and geochemical techniques, including thin section description, X-ray diffraction (XRD), whole-rock chemical analysis, scanning electron microscopy (SEM), Cathodoluminescence (CL) imaging, electron probe analysis, fluid inclusions and isotopic analysis. These integrated petrographic and geochemical techniques were used to determine the diagenetic history of the sandstones and its impact on the reservoir quality. The tight deltaic sandstones of the T3x2 and T3x4 (second and fourth members of Xujiahe Formation) have undergone a significant and complicated series of diagenetic alterations and changes in geochemical composition. Strong mechanical and chemical compaction together with carbonate cementation destroyed almost all the primary pores and the secondary dissolution pores now dominate the pore space. The T3x4 sandstones experienced a more open diagenetic system at near-surface and eodiagensis resulted in higher porosity than seen in the T3x2 sandstones. Both the T3x2 and T3x4 sandstones experienced closed-system diagenesis during middle-late mesodiagenesis. The early diagenetic dissolution, which mainly occurred in the open geochemical system, produced secondary pores and provided kaolinite and some K+ needed for the subsequent illitization of kaolinite and K-feldspar. The late dissolution of K-feldspar and illitization of K-feldspar in T3x4 sandstones and T3x2 sandstones during the mesodiagenesis, produced some effective secondary pores in the closed geochemical system or in the focused fluid flow zone along fractures. The diagenetic characteristics, size and evolution of (open vs closed) diagenetic system, which were constrained by the depositional environment, deep burial depth and tectonic activity, can be used to predict the reservoir quality ahead of drilling