Formation Of Igneous Rocks Research Articles

Karst groundwater conservation based on hydrochemistry and isotope stable analysis in Obi Island, South Halmahera

Abstract This paper presents an analysis of the hydrogeological characteristics of the Kelo karst area in Obi Island, South Halmahera, focusing on hydrochemistry and isotopic methods to delineate the groundwater recharge zones and propose conservation measures. Despite its natural state, the Kelo karst area has not been previously studied for hydrogeology nor exploited for resources. Unregulated exploitation of karst areas poses significant environmental risks, leading to the degradation of their strategic and hydrological functions. This study investigates spring characteristics through hydrochemistry analysis, stable isotopes (δ18O and δ2H), and groundwater mixing processes. Hydrochemistry and isotopic analyses elucidate the hydrogeological features, including groundwater origin and recharge mechanisms. The predominant groundwater facies in the study area exhibit a Ca-Mg-HCO3 − composition, reflecting the dissolution processes of both limestone and igneous rock formations. Isotopic analysis and local meteoric water line examination indicate a recharge zone elevation ranging from 612 to 945 meters. Geological features such as fracture zones, lineaments, faults, and sinkholes significantly influence the determination of recharge areas. Protection of these recharge zones is imperative for groundwater conservation, ensuring the sustained availability and quality of groundwater amidst the development pressures on karst landscapes.

Key Technology for Leak Prevention of Igneous Rocks in a Certain Oilfield in Bo Zhong

A certain oilfield in Bozhong has experienced multiple volcanic eruptions, with developed fractures in igneous rocks and frequent drilling leaks; In the early stage, 7 out of 8 exploration wells experienced 23 leaks, resulting in losses of over 24 million yuan. In response to the high risk of leaks in the igneous rock development area of this block, based on the concept of geological engineering integration, an innovative key technology for preventing leaks in igneous rocks in a certain oilfield in Bozhong was proposed, with "pre drilling prevention, monitoring while drilling, and rapid plugging" as the core. Through 30 on-site construction operations, a new operational approach was provided for the problem of leaks in igneous rock formations, effectively reducing drilling risks and costs.

MINERALOGICAL, PETROGRAPHIC AND GEOCHEMICAL EVIDENCE FOR ZIRCON FORMATION CONDITIONS WITHIN THE BURPALA MASSIF, NORTHERN BAIKAL REGION

This paper reports investigation on zircons from quartz syenite, alkaline and foid syenite, as well as metasomatic rock from the fenitization zone hosted by the Burpala massif. It is performed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), cathodoluminescence (CL), laser ablation inductively coupled plasma mass spectrometry (LA ICP MS), and Raman spectroscopy. Generally, all zircons from igneous rocks show rhythmic, crystal growth zoning or sector zoning (type I) except for some zircons from alkaline syenites (type II) showing patchy zoning. They systematically contain pores or cavities. The REE patterns of magmatic zircons share similar features: e.g. depletion of LREE ((Yb/La)N up to 35000), large positive Ce (Ce/Ce* 6–427) and small negative Eu (Eu/Eu* 0.37–0.93) anomalies. Zircons crystallized from quartz syenites at 830±30 °C at the early stage of rock formation, while zircons from alkaline and foid syenites crystallized at the later stage of rock formation (680–750 °C). Meanwhile, crystallization of zircons with rhythmic zoning (type I) occurs at later magmatic stage, while the formation zircons of type II is probably related to the separation of the highly fluorinated aqueous fluid from the residual melt.Zircons from fenites have a bipyramidal habit holding a heterogeneous mosaic core and a homogeneous (or rhythmic zoning) rim. The cores of zircon show flat REE patterns without significant anomalies, while the rims are characterized by noticeable fractionation of REE ((Yb/La)N 85–615) and show a positive Ce anomaly (Ce/Ce* 4–18). The Raman spectra of the cores show a higher degree of crystallinity than the rims, and their flat REE spectra are probably related to the contamination by micro inclusions. The discordant U-Pb age of 295±3 Ma was obtained for zircon rims, which is consistent with the age of formation of igneous rocks of the Burpala massif (298–291 Ma). The latter supports the syngenetic origin of metasomatic ore mineralization with the main stage of massif formation.

Early Paleozoic tectonic affinity of the Lesser Xing'an–Zhangguangcai Range, NE China: A continental arc along the western margin of the Jiamusi Block

The Lesser Xing'an–Zhangguangcai Range (LXZGCR) in NE China was traditionally interpreted to be the eastern part of the Songliao–Xilinhot Accretionary Terrane, separated from the Jiamusi–Khanka Block to the east by the Heilongjiang Complex. However, recent studies have shown that the Heilongjiang Complex formed in the late Paleozoic–early Mesozoic. Therefore, the tectonic affinity of the LXZGCR during the early Paleozoic remains unclear. To constrain this key issue, we present new zircon UPb ages, Hf isotopic compositions, and whole-rock geochemical data for early Paleozoic igneous rocks in the LXZGCR. The new ages, along with previously published data, suggest that the early Paleozoic magmatism in the LXZGCR can be divided into four stages: Middle–Late Cambrian (523–486 Ma), Early Ordovician (485–469 Ma), Late Ordovician (464–443 Ma), and Late Silurian (433–423 Ma). Middle–Late Cambrian igneous rocks are dominated by calc-alkaline I-type granitoids and high-Mg andesite–dacite–rhyolite association. Early Ordovician igneous rocks consist of a suite of calc-alkaline diorites, granodiorites, monzogranites, alkali-feldspar granites, and rhyolites, with I-type affinities. Late Ordovician igneous rocks consist mainly of I-type granitoids with minor A-type granitoids and rhyolites. Late Silurian igneous rocks are composed of calc-alkaline I-type granitoids with minor dacites. The early Paleozoic granitoids and felsic volcanic rocks originated from partial melting of dominantly Paleoproterozoic–Mesoproterozoic lower crust, whereas the Late Cambrian high-Mg andesite–dacite–rhyolite association was probably derived from partial melting of a depleted mantle wedge metasomatized by subduction-related fluids. The rock associations and geochemical characteristics suggest that these early Paleozoic igneous rocks formed in active continental margin and back-arc extension settings. Comparing the early Paleozoic magmatism, zircon Hf isotopic compositions, Nd model ages, and Precambrian basement features of the LXZGCR and the Jiamusi Block suggest that the LXZGCR was part of the same tectonic unit as the Jiamusi Block during the early Paleozoic. We argue that the formation of the early Paleozoic igneous rocks in the LXZGCR was related to the eastward subduction of a branch ocean of the Paleo-Asian Ocean beneath the Jiamusi–Khanka Block.

Progress in research on the exploration and evaluation of deep geothermal resources in the Fujian-Guangdong-Hainan region, China

Deep geothermal resources in the Fujian-Guangdong-Hainan region, China, offer significant potential for sustainable energy. The diverse igneous rock formations along the southeast coast present intricate geological challenges that impede exploration and evaluation efforts. In this study, we address critical concerns related to the Fujian-Guangdong-Hainan region's deep geothermal resources, encompassing heat source composition, formation conditions, strategic favorable areas, and exploration directions. Our methods involve the analysis of regional geothermal reservoirs and cap rocks. Major findings include: the primary heat sources in the Fujian-Guangdong-Hainan region consist of the radioactive heat generation from granites in the crust, heat conduction in the mantle, and, in specific areas like Yangjiang and Shantou, melts within the middle and lower crust; the deep, high-temperature geothermal resources in the region predominantly reside in basins' depressed areas. These areas are characterized by the confluence of triple heat sources: heat from the Earth's crust, mantle, and other supplementary sources; our analysis led to the identification of three strategic areas favorable for deep geothermal resources in the Fujian-Guangdong-Hainan region. These are the Beibu Gulf Basin's continental area, the Yuezhong Depression, and the Fuzhou-Zhangzhou area.

Petrogenesis of the Granitic Dykes in the Yangshan Gold Belt: Insights from Zircon U-Pb Chronology, Petrography, and In-Situ Hf Isotope Analysis

The Yangshan gold belt is renowned for its igneous rock formations, particularly dykes that form in tectonically weak zones. Some of these rock formations exhibit a close spatial relationship with gold mineralization, and a tiny portion of the granitic dykes serve as gold ore bodies by themselves. In order to investigate the nature of granitic dykes and their association with gold mineralization, we conducted a comprehensive study consisting of zircon U-Pb chronology, petrography, and in situ Hf isotope analysis of 25 granitic dyke samples collected from east to west across the belt. According to LA-ICP-MS zircon U-Pb dating results, the granitic dykes inherited zircon ages that are concentrated between 745.0 and 802.0 Ma, and magmatic intrusion ages that mainly fall between 201.0 and 213 Ma. Moreover, the granitic dykes display a calc-alkaline to high-K calc-alkaline peraluminous series, which is relatively enriched in light over heavy REE, with moderate Eu anomalies. These dykes are rich in large-ion lithophile elements and poor in high-field-strength elements. The zircon Lu-Hf isotope data range from εHf(t) values of −1.5 to 0.1, mantle model (TDM1) ages range from 859 to 937 Ma, and crustal model (TDM2) ages range from 1111 to 1218 Ma. The granitic dykes found in the Yangshan gold belt were formed between 200 and 213 Ma ago, during a period of intracontinental extension following the late collision between the Yangtze plate and Qinling microplates. These dykes originated from the volcanic basement of the Mesoproterozoic Bikou Group, which was formed by the melting of the upper crust under the crustal thickening caused by the subduction and collision of the Qinling microplate. Subsequently, the dykes were transported along a tectonically weak zone, assimilating surrounding rocks and undergoing a transformation from “I”-type to “S”-type granite before finally evolving into granite with specific “A”-type characteristics. Our study provides new insights into the petrogenesis of granitic dykes in the Yangshan gold belt, as well as the relationship between gold mineralization and magmatic activity, which has significant implications for mineral exploration and the geological understanding of gold mineralization in this region.

MAGMATIC ROCKS OF THE TEKTURMASS ACCRETIONARY COMPLEX, CENTRAL KAZAKHSTAN: GEOLOGICAL POSITION AND GEODYNAMIC SETTINGS OF FORMATION

The paper provides an overview of the geological structure and presents new data on petrography and geochemistry of igneous rocks of the Tekturmas accretionary complex (TAC). Consideration is being given to the age, petrogenesis and probable tectonic settings of formation of igneous rocks. It is shown that the TAC and adjacent ophiolite belt are parts of the Late Cambrian – Ordovician Pacific-type orogenic belt formed at an active margin of the Paleo-Asian Ocean. The TAC is dominated mainly by tholeiitic mafic igneous rocks (basalt, dolerite, gabbro). There are recognized three groups of rocks: high-Ti, medium-Ti and low-Ti. Geological and geochemical features of TAC igneous rocks suggest their formation in three tectonic settings: mid-ocean ridge (medium-Ti), oceanic island/seamount (high-Ti) and over subduction zones (low-Ti).

Petrography, Geochemical Features and Absolute Dating of the Mesozoic Igneous Rocks of Medvedev and Taezhniy Massifs (Southeast Russia, Aldan Shield)

The paper presents the results of the petrographic and geochemical studies of igneous rocks of the Medvedev and Taezhniy massifs, including their first absolute dating. The massifs are located in central Nimnyr block of the n shield within the Leglier ore cluster of the Evotinskiy ore district (Southeast Russia, Aldan Shield). For the first time, the three-phase structure of the Medvedev massif has been defined, as observed in our expedition and petrographic studies. Rocks from the three phases of the Medvedev massif include quartz syenites, syenites, and monzonites, and rocks from the two phases of the Taezhniy massif include quartz monzonites and syenites. Geochemically, the rocks are close to volcanic island arcs, the formation of which was related by subducted oceanic crust of the Mongol–Okhotsk Ocean. The defined duality of the geochemical compositions of the igneous rocks of the massifs may be due to the presence of both mantle and crustal sources; however, it is most likely that these rocks resulted from the melting of a mixed mantle source or the latter was contaminated by the crust with further differentiation of melts in intermediate crust chambers. Additionally, geochemical characteristics suggest that the analyzed rocks are close to latite and shoshonite derivatives and can be considered as part of the monzonite–syenite formation type. The first identified periods of formation of igneous rocks in the Medvedev massif are 122.0–118.0 Ma and Taezhniy 117.5–114.5 Ma, which correspond to the Early Cretaceous (Aptian).

A Method for Evaluating the Rock Breaking Efficiency of Cutters and Optimizing the PDC Cutter Profile—A Study of Igneous Rock Formations in Shunbei Oilfield

The Permian igneous rock in Shunbei Oilfield exhibits high rock strength, which results in a low rate of penetration (ROP) and shortens the cutter’s service life. It is necessary to analyze and evaluate the rock breaking effect of cutters. However, at this stage, the evaluation of the rock breaking effect has been limited to comparing the sizes of the mechanical specific energy (MSE), and the change in the rock breaking efficiency caused by the difference in the shape of the cutters’ surface has not been considered. Therefore, through the establishment of numerical simulation models of a circular cutter, bevel cutter, axe cutter, wedge cutter, and triangular cutter, the evaluation of the rock breaking efficiency of special-shaped cutters was completed. The results show that the triangular cutter and the wedge cutter are suitable for the front row cutter of the polycrystalline diamond compact bit (PDC); the triangular cutter is suitable for drilling into medium–hard formations, the wedge cutter is suitable for drilling into hard formations, and the bevel cutter is suitable for the back row cutter of the PDC, to assist other cutters in the process of rock breaking. The research results can provide the basis for the selection of PDC bit cutters and the design optimization of the bit.

Study on Rock Mechanics and Wellbore Stability of Igneous Formation in the Shunbei Area.

While drilling into the igneous rock formations of the Shunbei area, problems such as loss of well circulation and borehole collapse occur frequently, seriously hindering the efficient development of oil and gas resources. Aiming to solve this problem, the physicochemical and mechanical properties of igneous rocks are studied through a series of laboratory tests to determine the main factors influencing formation collapse and instability. In addition to the laboratory results, the weak plane effect of fracture mechanics, the seepage effect of drilling fluid, and the hydration effect of the drilling fluid on the borehole wall stability of igneous rock formations are evaluated and analyzed by establishing a mathematical model. The results show that the microfractures in the igneous rock are relatively developed and can be divided into unfilled fractures and calcite-filled fractures. The mechanical strength of the matrix igneous rock is higher than that of the rock samples with microfractures. The compressive strength of calcite-filled and unfilled fracture samples is 1/3–1/4 that of matrix igneous rocks, and immersion in the drilling fluid has little influence on the mechanical strength of igneous rocks. The fracture weak plane effect has the greatest influence on wellbore stability. With the increase of the number of fractures at different angles, the collapse pressure equivalent density of the formation subject to the mechanical weak plane effect increases by 21% compared with that of the homogeneous formation without fractures. The seepage effect of the drilling fluid on borehole stability is secondary, and the equivalent density of the formation collapse pressure increases by 11%. Because of the low content of clay minerals, the hydration effect of the drilling fluid on borehole stability was minimal and the equivalent density of collapse pressure increased by only 2%. During the drilling process, considering the weak plane effect of the microfractures and the seepage effect of the drilling fluid, the drilling fluid density should be controlled at about 1.82 g/cm3. The effective plugging ability and rheological properties of the drilling fluid should be improved for the formation with microfractures. The research results can provide a theoretical basis for the safe and efficient development of igneous reservoirs.

Influencing mechanics and correction method of nuclear magnetic resonance measurement in igneous rocks reservoir

Nuclear magnetic resonance (NMR) measurement provides lithology-independent porosity and pore structure for sedimentary reservoirs. Recently, oil and gas were discovered in igneous rock formations, however, NMR logging porosity is substantially lower than the true porosity, and the T2 distributions does not characterize the pore-size distributions. These observations limit the use of NMR logging in igneous rock formations and new research is needed to be developed. To address this gap in the literature, using numerical simulation of NMR behavior, we conduct a theoretical study to examine the impact of magnetic susceptibility, echo spacing, and fluid type on the T2 distributions in igneous rock. The simulation results and laboratory experiment show that, the paramagnetic minerals affect the magnetization of fluids in pores and rate of the echo decay, and NMR porosity is thus significantly reduced. To effectively correct the NMR measurement, a new approach is proposed to improve the underestimation of NMR porosity and T2 distribution shifting to shorter times. For a pore model, the corrected porosity and T2 distribution are both in good agreement with the model. In a case study from Chepaizi area of Junggar Basin, China, the corrected NMR porosity matches well with core measurement, and the corrected T2 distribution shifts to longer times more than before. Moreover, bound fluid volume and movable fluid volume are both corrected, and the NMR permeability also agrees well with core laboratory measurement, which proves that the correction method effective. Therefore, this technology enables NMR log for evaluating the igneous rock reservoir quality.

Effect of parameter correlation on risk analysis of wellbore instability in deep igneous formations

A Permian igneous formation in the Sichuan Basin typically exhibits complex lithology, strong heterogeneity, and strong uncertainty; consequently, there is a very high risk of wellbore collapse during drilling and completion, which would seriously affect the safety, efficiency, and cost of drilling operations. Therefore, to prevent wellbore collapse in Permian igneous rock formations, a risk assessment method of wellbore instability based on reliability theory was proposed, and the effects of parameter correlation on the reliability of wellbore stability were considered. First, profiles of the rock mechanical parameters, formation pore pressure, and in-situ stresses were established by logging interpretation. Second, the optimal probability distribution of each parameter was determined for three typical igneous formations, and the correlation coefficient matrix was obtained using correlation analysis. Third, the effect of parameter correlation was involved to propose a risk analysis method of wellbore instability, where the Monte Carlo method was used for random sampling. Finally, the safe mud weight window of each igneous formation was determined, and the sensitivity of wellbore stability to the parameter mean values and correlation coefficients was analyzed. The results indicate that significant uncertainty and parameter correlation exist for the igneous formations, which clearly affect wellbore stability. The effect is greatest for the breccia formation, followed by the tuff and basalt formations. The correlations between cohesion and internal friction angle and between cohesion and maximum horizontal principal stress are the most important factors affecting collapse pressure, whereas the correlation between the two horizontal stresses is most important for fracture pressure. The results suggest that the effect of parameter correlation on the reliability of wellbore stability in strongly heterogeneous settings cannot be ignored.

Modelling igneous rock mechanics parameter based on logging data in Shunbei oil field

In order to improve the rate of penetration (ROP) in Permian igneous rock strata, the rock mechanics is modeled based on the continuous logging data (acoustic, density, caliper, resistivity and gamma logging) and confirmatory indoor experiments. The model considers the influence of well collapse and expansion on logging data in igneous rock formation to improve the calculation accuracy. Based on this model, the continuous profile of Permian compressive strength, tensile strength, mud content, internal friction angle are calculated, and then the differences of Permian strata in the north, middle and south of the oilfield are further compared and analyzed. The results can provide support for the optimization of efficient rock breaking and reservoir fracturing technology.

The importance and status of the micronutrient selenium in South Africa: a review.

Selenium (Se) is a vital micronutrient with widespread biological action but leads to toxicity when taken in excessive amounts. The biological benefits of Se are mainly derived from its presence in active sites of selenoproteins such as glutathione peroxidase (GPx). An enzyme whose role is to protect tissues against oxidative stress by catalysing the reduction of peroxidase responsible for various forms of cellular damage. The benefits of Se can be harvested when proper regulations of its intake are used. In South Africa, Se distribution in people's diets and animals are low with socio-economic factors and heterogeneous spread of Se in soil throughout the country playing a significant role. The possible causes of low Se in soils may be influenced by underlying geological material, climatic conditions, and anthropogenic activities. Sedimentary rock formations show higher Se concentrations compared to igneous and metamorphic rock formations. Higher Se concentrations in soils dominates in humid and sub-humid areas of South Africa. Furthermore, atmospheric acid deposition dramatically influences the availability of Se to plants. The studies reviewed in this article have shown that atomic absorption spectroscopy (AAS) is the most utilised analytical technique for total Se concentration determination in environmental samples and there is a lack of speciation data for Se concentrations. Shortcomings in Se studies have been identified, and the future research directions of Se in South Africa have been discussed.

Mechanical characteristics and influencing factors of shallow igneous rocks in Junggar Basin

The mechanical properties of rocks play a pivotal role in hydraulic fracture propagation. In this study, mineral composition experiments, uniaxial and triaxial tests, shear tests, and fracture toughness tests were performed to analyze the rock mechanics characteristics of igneous rocks and their relationship with confining pressure, mineral composition, lithology, and lithofacies. The results show that the confining pressure has a significant influence on the elastic modulus and compressive strength of the igneous rock, but an insignificant effect on Poisson’s ratio. The contents of clay minerals and brittle minerals significantly affect the mechanical properties. However, the lithology and lithofacies do not have an evident influence on the rock mechanical properties. In this study, a dimensionless elastic modulus, namely, the ratio of the elastic modulus to the confining pressure is proposed. The average dimensionless elastic modulus under different confining pressures exhibited a good linear correlation with the confining pressure. This parameter can be used to predict the elastic modulus. The results of this study can provide a basis for the hydraulic fracturing design of shallow igneous rock formations in the Junggar Basin in China.

AGE CONSTRAINTS AND METALLOGENIC PREDICTION OF GOLD DEPOSITS IN THE AKZHAL-BOKO-ASHALIN ORE ZONE (ALTAI ACCRETION-COLLISION SYSTEM)

We present new age constraints for igneous rocks and ore-metasomatic formations of the gold deposits in the Akzhal-Boko-Ashalin ore zone. In terms of their ore formation, these deposits correspond mainly to the orogenic type, which generally reflects specific metallogeny of the West Kalba gold-bearing belt in East Kazakhstan. Gold-quartz veins and mineralized zones of the gold-sulphide formation are confined to fractures feathering regional NW-striking and sublatitudinal faults. Their common features include the following: gold-bearing veinlet-disseminated pyrite-arsenopyrite ores that are localized in carbonaceous-sandy-schist and turbidite strata of different ages; structural-tectonic control of mineralization, numerous dikes of medium-basic compositions in ore-control zones; and the presence of post-orogenic heterochronous granite-granodiorite rocks, although their relation to gold-ore mineralization is not obvious. Igneous rocks of the study area have similar ages in a narrow range from 309.1±4.1 to 298.7±3.2 Ma, which is generally consistent with the previously determined age of granitoid massifs of gold-ore fields in East Kazakhstan. A younger age (292.9±1.3 to 296.7±1.6 Ma) is estimated for felsic rocks of the dyke complex. For the ore mineralization, the 40Ar/39Ar dating of sericite from near-ore metasomatites yields two age intervals, 300.4±3.4 Ma and 279.8±4.3 Ma. A gap between of the ages of the ore mineralization and the igneous rocks is almost 20 Ma, which may indicate that the processes of ore formation in the ore field continued in an impulse-like pattern for at least 20 Ma. Nevertheless, this confirms a relationship between the hydrothermal activity in the study area and the formation and evolution of silicic igneous rocks of the given age interval, which belong to the Kunush complex, according to previous studies. This interpretation is supported by reconstructed tectonic paleostress fields, showing that directions of the main normal stress axes changed during the ore mineralization stage, which is why the ore bodies significantly differ in their orientations. The above-mentioned data are the first age constraints for the study area. Additional age determinations are needed to further improve understanding of the chronology of ore-forming processes. Actually, all the features characterizing the gold mineralization of the Akzhal, Ashalin and Dauba ore fields, including the data on lithology, stratigraphy, structural tectonics, magmatism, isotope geochronology, mineralogy and geochemistry, can be used as criteria when searching for similar ore fields in East Kazakhstan.

ГРАНИТОИДНЫЕ МАССИВЫ ЗОНЫ ПЕРЕХОДА ОКИСЛИТЕЛЬНО-ВОССТАНОВИТЕЛЬНЫХ УСЛОВИЙ (СИХОТЭ-АЛИНЬСКИЙ ОРОГЕННЫЙ ПОЯС)

Redox conditions for the formation of igneous rocks determine the valence of variable valence elements. The ore mineral composition and amount, the magnetic fraction weight and the magnetic susceptibility of the rock and the composition of the dark-colored minerals depend on the ratio of Fe3+ and Fe2+. It is for the first time for more than 50 years of the redox conditions study that the he authors obtained detailed data on granitoid massifs located in the zone of redox conditions transition.

Wellbore Stability Mechanism and Countermeasures of Igneous Formations in Shunbei Oilfield

Shunbei oilfield is located in the Midwest of Tarim Basin. Since 2018 many wells in the block have encountered broken formation, directional wells wellbore collapsed seriously, resulting drilling sidewells, with a huge loss of drilling costs. The influencing factors of igneous formation stability include internal and external factors. The internal cause refers to the formation instability caused by the strength anisotropy and strong in-situ stress nonuniformity of igneous formation. The external cause refers to various factors that cause the change of the external environment of the formation caused by drilling engineering, including the physical and chemical interaction between the drilling fluid and the formation, well trajectory and mechanical disturbance of the drilling string, etc. Based on the analysis of the influencing factors of wellbore stability in igneous rock, the technical countermeasures of wellbore stability in igneous rock formation are put forward and field tests are carried out. In the Permian fractured formation of Shunbei oil field,the idea of “prevention first, combination of prevention and blocking” is adhered to the first principles. Low density and low viscosity drilling fluid with low displacement is adopted to prevent the occurrence of lost circulation. The wellbore of the igneous rock intrusion in santamu formation of Ordovician is easy to collapse. By adopting special sealing structure and strengthening plugging and anti-collapse, combined with slurry plugging and well washing and refining engineering measures, the safe drilling of the igneous rock can be ensured.

Lost Circulation Mechanical Model and It’s Application in Permian Igneous Rocks in Shunbei Oilfield

The Shunbei Oilfield is a major discovery of Sinopec in the ultra-deep marine carbonate rock field, and it will become the main battlefield for Sinopec to increase reserves and production. At present, the exploration and development of the Shunbei Oilfield is mainly concentrated on the No. 1 and No. 5 fault zones in the Shunbei area. Due to the complex geological structure, there are a series of drilling technical problems in drilling. Lost circulation will not only lose drilling fluid, produce non-productive time and affect drilling safety, but also limit drilling speed, which is one of the most headaches and difficult problems in drilling. To this end, scholars at home and abroad have carried out a lot of research and exploration, and developed a series of leak-proof and plug-in devices such as non-penetrant, elastic graphite, Form-A-block, fiber cement, water-absorbing resin, thermosetting resin, gel and chemical consolidation. Materials, and formed a variety of supporting process technologies. Granular, fibrous, and sheet composite bridging materials are most commonly used on the site, but ordinary bridging materials are resistant to temperature differences, easily carbonized at high temperatures, and the width of underground cracks needs to be clear when plugging, non-penetrants prevent Lost circulation of microfracture formations. It has poor leak-proof effect on large cracks, because of its low strength, expansion materials such as water-absorbent resin are better for plugging, but the pressure-bearing effect is poor, foreign Form-A-block and Chinese DTR are equivalent High water loss materials have good adaptability to cracks, but the pressure is generally low, fiber plugging methods such as fiber cement and thermosetting resin are complicated in process, high in risk and high in cost, gel plugging technology has good adaptability to plugging, but withstands temperature differences If it is not combined with other materials, it is easy to leak again in the later period due to the decrease in gel strength, chemical consolidation plugging technology has a high success rate in plugging, but the plugging construction time is relatively long. In summary, although great progress has been made in leak prevention and plugging technology at home and abroad, there is less research on igneous rocks, and it cannot meet the needs for leak prevention and plugging in igneous rock formations. Therefore, it is necessary to analyze the second Shunbei Oilfield in depth. Lost circulation characteristics of igneous rocks in the Mesozoic and the difficult points of preventing Lost circulation and plugging. Develop effective materials for preventing and plugging Lost circulation to improve the effect of preventing and plugging.

Zircon melt inclusions in mafic and felsic rocks of the Bushveld Complex – Constraints for zircon crystallization temperatures and partition coefficients

Melt inclusions in zircon represent time capsules, which provide deep insights into igneous rock formation including timing, physicochemical conditions, and the compositional evolution of cogenetic magmas with respect to major, trace, and volatile elements. However, their full potential as petrogenetic indicators, in particular their usability and consistency as geothermometers, is poorly investigated. Therefore, we present new mineralogical and chemical data for recrystallized and homogenized melt inclusions and host zircon from different mafic and felsic rocks of the Bushveld Complex (BC), South Africa. Samples include rutile-bearing cumulate rocks of the Marginal and Critical zones, as well as rutile-free, magnetite-ilmenite-titanite-bearing diorites and granites of the Upper Zone, Rashoop Granophyre and Lebowa Granite Suite. All melt inclusions, irrespective of rock type, have rhyolitic compositions with SiO2 contents ranging from 65 to 78 wt.%, and H2O from 1.6 to 4.0 wt.%, whereas trace element contents differ systematically between rock types. In rutile-bearing mafic rocks, melt inclusions commonly show higher Ti contents (>800 ppm), higher Th/U ratios (up to 38), and lower REE contents (ƩREE < 150 ppm) compared to those in rutile-free mafic and felsic rocks (Ti < 800 ppm; Th/U < 5; ƩREE > 150 ppm). Liquidus temperatures of melt inclusions obtained from normative Qz-Ab-Or and rhyolite-MELTS modelling indicate melt entrapment mostly at 930–850 °C (at 200 MPa), tailing down in some samples to 700 °C. For rutile-bearing rocks, these temperatures overlap with those obtained by TiO2-in-melt and Ti-in-zircon geothermometry. For all rutile-free mafic and felsic rocks, reduced TiO2 activities of aTiO2 ∼ 0.3 are required for Ti-in-zircon geothermometry, and TiO2rutile ∼ 30 wt.% for TiO2 saturation geothermometry, to match temperatures from other geothermometers. Furthermore, partition coefficients obtained from melt inclusion - host zircon pairs are within error identical for mafic and felsic rocks and also reveal no systematic dependency on melt inclusion size, composition and entrapment temperature. The results of this study demonstrate that melt inclusions in zircon are a powerful tool for geothermometry and to constrain magma compositions, H2O contents, and TiO2 activities, which are critical for the understanding of magmatic processes shaping Earth’s crust.