Petroleum Exploration and Development最新文献

Based on the waterflooding development in carbonate reservoirs in the Middle East, in order to solve the problem of the poor development effects caused by commingled injection and production, taking the thick bioclastic limestone reservoirs of Cretaceous in Iran-Iraq as an example, this paper proposes a balanced waterflooding development technology for thick and complex carbonate reservoirs. This technology includes the fine division of development units by concealed baffles and barriers, the combination of multi well type and multi well pattern, and the construction of balanced water injection and recovery system. Thick carbonate reservoirs in Iran-Iraq are characterized by extremely vertical heterogeneity, development of multi-genesis ultra-high permeability zones, and highly concealed baffles and barriers. Based on the technologies of identification, characterization, and sealing evaluation for concealed baffles and barriers, the balanced waterflooding development technology is proposed, and three types of balanced waterflooding development modes/techniques are formed, namely, conventional stratigraphic framework, fine stratigraphic framework, and deepened stratigraphic framework. Numerical simulations show that this technology is able to realize a fine and efficient waterflooding development to recover, in a balanced manner, the reserves of thick and complex carbonate reservoirs in Iran and Iraq. The proposed technology provides a reference for the development optimization of similar reservoirs.

This study conducted temporary plugging and diversion fracturing (TPDF) experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion with multi-cluster sand jetting perforation. The effects of temporary plugging agent (TPA) particle size, TPA concentration, single-cluster perforation number and cluster number on plugging pressure, multi-fracture diversion pattern and distribution of TPAs were investigated. A combination of TPAs with small particle sizes within the fracture and large particle sizes within the segment is conducive to increasing the plugging pressure and promoting the diversion of multi-fractures. The addition of fibers can quickly achieve ultra-high pressure, but it may lead to longitudinal fractures extending along the wellbore. The temporary plugging peak pressure increases with an increase in the concentration of the TPA, reaching a peak at a certain concentration, and further increases do not significantly improve the temporary plugging peak pressure. The breaking pressure and temporary plugging peak pressure show a decreasing trend with an increase in single-cluster perforation number. A lower number of single-cluster perforations is beneficial for increasing the breaking pressure and temporary plugging peak pressure, and it has a more significant control on the propagation of multi-cluster fractures. A lower number of clusters is not conducive to increasing the total number and complexity of artificial fractures, while a higher number of clusters makes it difficult to achieve effective plugging. The TPAs within the fracture is mainly concentrated in the complex fracture areas, especially at the intersections of fractures. Meanwhile, the TPAs within the segment are primarily distributed near the perforation cluster apertures which initiated complex fractures.

Based on new data from cores, drilling and logging, combined with extensive rock and mineral testing analysis, a systematic analysis is conducted on the characteristics, diagenesis types, genesis and controlling factors of deep to ultra-deep abnormally high porosity clastic rock reservoirs in the Oligocene Linhe Formation in the Hetao Basin. The reservoir space of the deep to ultra-deep clastic rock reservoirs in the Linhe Formation is mainly primary pores, and the coupling of three favorable diagenetic elements, namely the rock fabric with strong compaction resistance, weak thermal compaction diagenetic dynamic field, and diagenetic environment with weak fluid compaction-weak cementation, is conducive to the preservation of primary pores. The Linhe Formation clastic rocks have a superior preexisting material composition, with an average total content of 90% for quartz, feldspar, and rigid rock fragments, and strong resistance to compaction. The geothermal gradient in Linhe Depression in the range of (2.0–2.6) °C/100 m is low, and together with the burial history of long-term shallow burial and late rapid deep burial, it forms a weak thermal compaction diagenetic dynamic field environment. The diagenetic environment of the saline lake basin is characterized by weak fluid compaction. At the same time, the paleosalinity has zoning characteristics, and weak cementation in low salinity areas is conducive to the preservation of primary pores. The hydrodynamic conditions of sedimentation, salinity differentiation of ancient water in saline lake basins, and sand body thickness jointly control the distribution of high-quality reservoirs in the Linhe Formation.

Based on the independently developed true triaxial multi-physical field large-scale physical simulation system of in-situ injection and production, we conducted physical simulation of long-term multi-well injection and production in the hot dry rocks of the Gonghe Basin, Qinghai Province, NW China. Through multi-well connectivity experiments, the spatial distribution characteristics of the natural fracture system in the rock samples and the connectivity between fracture and wellbore were clarified. The injection and production wells were selected to conduct the experiments, namely one injection well and two production wells, one injection well and one production well. The variation of several physical parameters in the production well was analyzed, such as flow rate, temperature, heat recovery rate and fluid recovery. The results show that under the combination of thermal shock and injection pressure, the fracture conductivity was enhanced, and the production temperature showed a downward trend. The larger the flow rate, the faster the decrease. When the local closed area of the fracture was gradually activated, new heat transfer areas were generated, resulting in a lower rate of increase or decrease in the mining temperature. The heat recovery rate was mainly controlled by the extraction flow rate and the temperature difference between injection and production fluid. As the conductivity of the leak-off channel increased, the fluid recovery of the production well rapidly decreased. The influence mechanisms of dominant channels and fluid leak-off on thermal recovery performance are different. The former limits the heat exchange area, while the latter affects the flow rate of the produced fluid. Both of them are important factors affecting the long-term and efficient development of hot dry rock.

Based on the data of outcrop, core, logging, gas testing, and experiments, the natural gas accumulation and aluminous rock mineralization integrated research was adopted to analyze the controlling factors of aluminous rock series effective reservoirs in the Ordos Basin, NW China, as well as the configuration of coal-measure source rocks and aluminous rock series reservoirs. A natural gas accumulation model was constructed to evaluate the gas exploration potential of aluminous rock series under coal seam in the basin. The effective reservoirs of aluminous rock series in the Ordos Basin are composed of honeycomb-shaped bauxites with porous residual pisolitic and detrital structures, with the diasporite content of greater than 80% and dissolved pores as the main storage space. The bauxite reservoirs are formed under a model that planation controls the material supply, karst paleogeomorphology controls diagenesis, and land surface leaching improves reservoir quality. The hot humid climate and sea level changes in the Late Carboniferous–Early Permian dominated the development of a typical coal-aluminum-iron three-stage stratigraphic structure. The natural gas generated by the extensive hydrocarbon generation of coal-measure source rocks was accumulated in aluminous rock series under the coal seam, indicating a model of hydrocarbon accumulation under the source. During the Upper Carboniferous–Lower Permian, the relatively low-lying area on the edge of an ancient land or island in the North China landmass was developed. The gas reservoirs of aluminous rock series, which are clustered at multiple points in lenticular shape, are important new natural gas exploration fields with great potential in the Upper Paleozoic of North China Craton.

This paper systematically reviews the current applications of various spatial information technologies in CO₂ sequestration monitoring, analyzes the challenges faced by spatial information technologies in CO₂ sequestration monitoring, and prospects the development of spatial information technologies in CO₂ sequestration monitoring. Currently, the spatial information technologies applied in CO₂ sequestration monitoring mainly include five categories: eddy covariance method, remote sensing technology, geographic information system, Internet of Things technology, and global navigation satellite system. These technologies are involved in three aspects: monitoring data acquisition, positioning and data transmission, and data management and decision support. Challenges faced by the spatial information technologies in CO₂ sequestration monitoring include: selecting spatial information technologies that match different monitoring purposes, different platforms, and different monitoring sites; establishing effective data storage and computing capabilities to cope with the broad sources and large volumes of monitoring data; and promoting collaborative operations by interacting and validating spatial information technologies with mature monitoring technologies. In the future, it is necessary to establish methods and standards for designing spatial information technology monitoring schemes, develop collaborative application methods for cross-scale monitoring technologies, integrate spatial information technologies with artificial intelligence and high-performance computing technologies, and accelerate the application of spatial information technologies in carbon sequestration projects in China.

An optimization method of fracturing fluid volume strength was introduced taking well X-1 in Biyang Sag of Nanxiang Basin as an example. The characteristic curves of capillary pressure and relative permeability were obtained from history matching between forced imbibition experimental data and core-scale reservoir simulation results and taken into a large scale reservoir model to mimic the forced imbibition behavior during the well shut-in period after fracturing. The optimization of the stimulated reservoir volume (SRV) fracturing fluid volume strength should meet the requirements of estimated ultimate recovery (EUR), increased oil recovery by forced imbibition and enhancement of formation pressure and the fluid volume strength of fracturing fluid should be controlled around a critical value to avoid either insufficiency of imbibition displacement caused by insufficient fluid amount or increase of costs and potential formation damage caused by excessive fluid amount. Reservoir simulation results showed that SRV fracturing fluid volume strength positively correlated with single-well EUR and an optimal fluid volume strength existed, above which the single-well EUR increase rate kept decreasing. An optimized increase of SRV fracturing fluid volume and shut-in time would effectively increase the formation pressure and enhance well production. Field test results of well X-1 proved the practicality of established optimization method of SRV fracturing fluid volume strength on significant enhancement of shale oil well production.

Based on the organic geochemical data and the molecular and stable carbon isotopic compositions of natural gas of the Lower Permian Fengcheng Formation in the western Central Depression of Junggar Basin, combined with sedimentary environment analysis and hydrocarbon-generating simulation, the gas-generating potential of the Fengcheng source rock is evaluated, the distribution of large-scale effective source kitchen is described, the genetic types of natural gas are clarified, and four types of favorable exploration targets are selected. The results show that: (1) The Fengcheng Formation is a set of oil-prone source rocks, and the retained liquid hydrocarbon is conducive to late cracking into gas, with characteristics of high gas-generating potential and late accumulation; (2) The maximum thickness of Fengcheng source rock reaches 900 m. The source rock has entered the main gas-generating stage in Penyijingxi and Shawan sags, and the area with gas-generating intensity greater than 20×10⁸ m³/km² is approximately 6 500 km². (3) Around the western Central Depression, highly mature oil-type gas with light carbon isotope composition was identified to be derived from the Fengcheng source rocks mainly, while the rest was coal-derived gas from the Carboniferous source rock; (4) Four types of favorable exploration targets with exploration potential were developed in the western Central Depression which are structural traps neighboring to the source, stratigraphic traps neighboring to the source, shale-gas type within the source, and structural traps within the source. Great attention should be paid to these targets.

Based on the geochemical parameters and analytical data, the heat conservation equation, mass balance law, Rayleigh fractionation model and other methods were used to quantify the in-situ yield and external flux of crust-derived helium, and the initial He concentration and thermal driving mechanism of mantle-derived helium, in the Ledong Diapir area, the Yinggehai Basin, in order to understand the genetic source, migration and accumulation mechanisms of helium under deep thermal fluid activities. The average content of mantle-derived He is only 0.001 4%, the ³He/⁴He value is (0.002–2.190)×10⁻⁶, and the R/R_a value ranges from 0.01 to 1.52, indicating the contribution of mantle-derived He is 0.09%–19.84%, while the proportion of crust-derived helium can reach over 80%. Quantitative analysis indicates that the crust-derived helium is dominated by external input, followed by in-situ production, in the Ledong diapir area. The crust- derived helium exhibits an in-situ ⁴He yield rate of (7.66– 7.95)×10⁻¹³ cm³/(a·g), an in-situ ⁴He yield of (4.10–4.25)× 10⁻⁴ cm³/g, and an external ⁴He influx of (5.84–9.06)×10⁻² cm³/g. These results may be related to atmospheric recharge into formation fluid and deep rock-water interactions. The ratio of initial mole volume of ³He to enthalpy (W) is (0.004–0.018) ×10⁻¹¹ cm³/J, and the heat contribution from the deep mantle (X_M) accounts for 7.63%–36.18%, indicating that deep hot fluid activities drive the migration of mantle-derived ³He. The primary helium migration depends on advection, while the secondary migration is controlled by hydrothermal degassing and gas-liquid separation. From deep to shallow layers, the CO₂/³He value rises from 1.34×10⁹ to 486×10⁹, indicating large amount of CO₂ has escaped. Under the influence of deep thermal fluid, helium migration and accumulation mechanisms include: deep heat driven diffusion, advection release, vertical hydrothermal degassing, shallow lateral migration, accumulation in traps far from faults, partial pressure balance and sealing capability.

Taking the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin as an example, the influences of the burial process in a foreland basin on the diagenesis and the development of high-quality reservoirs of deep and ultra-deep clastic rocks were investigated using thin section, scanning electron microscope, electron probe, stable isotopic composition and fluid inclusion data. The Qingshuihe Formation went through four burial stages of slow shallow burial, tectonic uplift, progressive deep burial and rapid deep burial successively. The stages of slow shallow burial and tectonic uplift not only can alleviate the mechanical compaction of grains, but also can maintain an open diagenetic system in the reservoirs for a long time, which promotes the dissolution of soluble components by meteoric freshwater and inhibits the precipitation of dissolution products in the reservoirs. The late rapid deep burial process contributed to the development of fluid overpressure, which effectively inhibits the destruction of primary pores by compaction and cementation. The fluid overpressure promotes the development of microfractures in the reservoir, which enhances the dissolution effect of organic acids. Based on the quantitative reconstruction of porosity evolution history, it is found that the long-term slow shallow burial and tectonic uplift processes make the greatest contribution to the development of deep–ultra-deep high-quality clastic rock reservoirs, followed by the late rapid deep burial process, and the progressive deep burial process has little contribution.