Calcium carbonate has attracted much attention due to its wide range of industrial applications. It is also considered to be the main scaly component in industrial water. Controlling the crystallization process of calcium carbonate is one of the main goals of research in many fields. The presence of foreign inorganic ions changes the rate of precipitation of calcium carbonate and also affects the nature and morphology of the precipitated phase. Combining research progress in recent years, the effects of inorganic ions on the crystallization process of calcium carbonate were reviewed. The effects of common metal cations and anions on the polymorphism and morphology of calcium carbonate were introduced. The mechanism of action was also analyzed, which provided theoretical support for the industrial application of calcium carbonate.
The technology of water plugging in the oil well is more and more concerned with its low cost, low damage and long period of validity. But in the application, it is found that the effect of water shutoff and profile control of active crude oil in different blocks is quite different. Plugging measures effect is obvious in some fields, while in the others, it is very poor. The reason is that the content of gum and asphaltene in crude oil components of different blocks is quite different, and this substance will have a great influence on the emulsification effect of active crude oil. In order to improve the level of active⁃crude⁃oil water plugging technology fundamentally, on the basis of extensive investigation and research, the influence factors of emulsifier structures and crude oil composition on oil⁃in⁃water emulsion are studied, through the laboratory emulsification experiment and spectral analysis. It is concluded that the longer the length of the oil⁃wet carbon⁃carbon single chain of the Span series of emulsifier, the greater the viscosity of the emulsion. The existence of double bond is not conducive to the formation of emulsion and the emulsion viscosity is low. The composition of 5 aromatic rings in the gum is conducive to the dissolution of asphaltenes, while the planar arrangement of 5 aromatic rings will increase the viscosity of the emulsion.
In order to further improve the recovery of oil after binary composite flooding in offshore oil fields,based on the development contradiction existing after the binary flooding,combined with the indoor physical simulation experiment,three different combinations of oil displacement systems were designed on the basis of conventional oil displacement agents. According to the characteristics of the reservoir after the binary flooding,three kinds of high concentration polymer flooding,high concentration polymer + two yuan and heterogeneous phase were proposed and compared with the experiment. The results showed that the three experimental schemes showed different degrees of secondary decline in water,the shunt rate of the high permeability layer decreased,and the shunt rate of the medium and low permeability layer increased.The recovery rate of experiment was 13.55%,10.93% and 16.05%,respectively.It provides technical support for subsequent profile optimization and individual well personalized design,which lays the foundation for the completion of a set of recovery technology method system after a set of two yuan flooding.
In order to accurately identify the leakage location of multi⁃annulus pressure wellbore in deep gas wells, field tests of leakage detection have been carried out for typical well X1 in X deep gas field in China by using array noise, spectrum noise, electromagnetic defect detection and temperature logging technology and through production tubing logging methods. The results show that there are leakage points in the A, B and C annulus of the well. The formation gas channeling through packers, casing threads and cement sheaths leads to continuous annulus pressure in the well. It can be seen that the combined logging technology can locate the deep gas well leakage point through the 3⁃layer pipe column, and comprehensive information can be used to accurately determine the path and cause of the gas leakage. The casing leakage was detected through the production tubing, so the leak detection results can not only provide an important basis for the treatment of the wells with sustained casing pressure, but also avoid tripping operation, without affecting gas well production, which has certain application prospects.
In order to clarify the fractal features of the pore structure of coal rock in Hancheng and Baode block, a new fractal characterization method was derived based on matchstick model. The new method was validated by scanning electron microscopy (SEM) and mercury intrusion test data. On this basis, the fractal characteristics of pore structure in medium and low coal rocks were studied. The results show that the matchstick model can more accurately characterize the dual pore structure of middle and low coal rank coal rocks. In the bi⁃logarithmic coordinate, the mercury saturation is in a bilinear relationship with the capillary pressure, that is, the pore structure of medium⁃low rank coal rocks has the fractal characteristics of sections, and the pores and cracks have different fractal intervals and fractal dimensions by the dividing line of 1 μm. The pores fractal dimension ranges from 2.80 to 2.98 and the crack fractal dimension ranges from 2.17 to 2.33 for Hancheng and Baode block. The fractal dimension of fracture for coal sample increases with the increase of the fractal dimension of pores, and both fractal dimensions decrease with the increase of average pore radius, porosity and permeability. Fractal dimension of coal rock is the key index of reservoir evaluation and can characterize the heterogeneity of its pore structure. The larger the fractal dimension is, the stronger the heterogeneity of pore structure is. The fractal dimension of cleavage and fracture is much larger than that of pore in Hancheng and Baode Block.
The uniaxial compression test of deep rock in three Zhaohe area of Daqing is carried out by using the 20 ton single axis test machine. Based on laboratory experimental mechanics, rock physical parameters and contact parameters can be measured by uniaxial compression. Simulated rock samples with similar mechanical properties as laboratory experiments can be obtained by calibrating virtual parameters of discrete element software. Uniaxial compression experiments of rock samples were carried out by EDEM simulation, and stress⁃strain curves were obtained. Based on the stress⁃strain curves, the staged failure process of rock under uniaxial stress was obtained. The staged failure morphology, micro⁃fracture characteristics of force chain and the relationship between the number of bond bonds and time at different time were studied. The results show that brittle rock has no large deformation during uniaxial compression, the mode of force chain fracture is direct fracture, and no great deformation occurs. The cause of this damage may be the result of the occurrence and development of cracks in rocks.
Through the analysis of stress sensitivity data of low permeability rock samples in the periphery of Daqing, it is found that the stress sensitivity of low permeability oil layer is greatly affected by permeability and effective stress, and the power relation can be used to better fit the relationship between permeability and effective pressure. According to the experimental analysis, the relationship between permeability and bottomhole pressure, oil well production and bottomhole pressure under the influence of stress sensitivity is derived, and the corresponding stress sensitivity map of low permeability reservoir in Daqing is drawn. Through numerical simulation, the effect of advanced water injection technology on the development of low permeability reservoirs was studied and relevant technical indicators were optimized.
In order to solve the technical problem of injected fluid channeling in offshore oilfields,the basic performance evaluation of plugging agent,core hole plugging rate and the large⁃scale dominant channel treatment experiment of "plugging + profile control" oil increase and precipitation effect was carried out in Bohai reservoir. The results show that the blocking rate of blocking agent for large⁃scale dominant channel is higher than 90%,which indicates that it can meet the technical requirements of blocking large⁃scale dominant channel in Bohai reservoir.Combining the large⁃scale dominant channel plugging technology with chemical profile control and flooding technology,the dual effects of macro and micro fluid flow diversion can be obtained,and the effect of oil increase and precipitation is very obvious.Compared with hydrophobically associating polymer solution,although the viscosity of Cr3+ polymer gel is relatively low,the polymer molecular aggregates in Cr3+ polymer gel have "intramolecular" cross⁃linking structure characteristics,and have better compatibility with reservoir pores,which can establish an effective displacement pressure gradient in deep core,resulting in better fluid diversion effect and larger recovery.
In view of the shortcomings of existing offshore drilling fluids,this paper optimizes common drilling fluid additives and combines sodium silicate with polymeric alcohols, and developes a high⁃blocking water⁃based drilling fluid with strong inhibition, lubricity and suitable for offshore drilling. The final formulation of seawater sodium silicate polyalcohol drilling fluid is: 400 mL seawater+5.0% bentonite+5.0% Na2CO3+0.4% PAC + 0.7% HA resin + 3.0% sodium silicate + 5.0% polyethylene glycol.The performance evaluation of sodium silicate polyalcohol drilling fluid showed that the apparent viscosity of the drilling fluid system was 30.4 mPa·s, the plastic viscosity was 20.3 mPa·s,the dynamic shear force was 13.1 Pa,and the rheological property was superior to the conventional marine drilling fluid system.The rolling recovery rate of the drilling fluid at 80 ℃ reach up to 87.5%,and the shale swelling height of the 8⁃hour soaking shale is 0.44 mm, which can solve the problem of wellbore stability. The experimental data of the anti⁃pollution ability test indicates that the drilling fluid has the ability to resist salt (Ca2+, etc).
At present, the main block of Changyuan in Daqing has entered the late period of development, with the characteristics of high water cut and high extraction degree. The remaining oil is highly dispersed, and the difficulty of adjusting the potential of tapping the potential is gradually increasing. In order to delineate the P reservoir area of the south west slope of A zone, the reservoir structure, reservoir and oil and water distribution are studied by means of logging seismic joint tectonic interpretation, reservoir prediction and oil and water identification. The research shows that the horizontal surface distribution of P oil reservoir is controlled by structural units, the type of vertical reservoir is controlled by the characteristics of sedimentary evolution, oil enrichment is controlled by fault sealing, and oil and gas accumulation is difficult to be determined by the relationship between fracture and sand body configuration. According to the research results, the potential area of I, II and III is delineated in the P oil layer of the west slope, and the total geological reserves are obtained.
Based on core, logging and logging data, the high⁃precision sequence stratigraphic framework in Nantun formation of Wunan subsag, Wuerxun depression, Hailar basin and the distribution characteristics of sedimentary systems under its control are studied. The results show that there are five types of sequence boundaries in Nantun formation, which can be divided into three third⁃order sequences and nine fourth⁃order sequences. Throughout the variation of residual stratum thickness of each sequence, it can be found that the sedimentation center of Nantun formation moved westward gradually, and the stratum distribution characteristics changed from "moderate thickness to east and west thin" to "west thick to east thin" gradually from bottom to top. During the sedimentary period of Nantun formation in Wunan subsag, four sedimentary systems were developed, including braided river delta, fan delta, sublacustrine fan and lake. Each sedimentary system has the characteristics of "east⁃west zoning". The fan delta sedimentary system mainly develops in the western Wuxi steep slope zone, and the braided river delta sedimentary system mainly develops in the eastern Wudong gentle slope zone. The distribution characteristics of sedimentary system in different periods have obvious inheritance.
Sublacustrine fan is a very important place for oil and gas accumulation in continental rift basins. Establishing an accurate and reliable sedimentary model of sublacustrine fan is of great significance to the prediction of dominant reservoirs. Based on the data of lithofacies, seismic profile facies, logging facies and grain size analysis, the sedimentary characteristics and models of sublacustrine fan depositional system developed in Nantun formation of lower cretaceous in Chaganuoer depression of Hailar Basin are systematically studied in this paper. It is considered that there are three subfacies and five microfacies in the sublacustrine fan depositional system of Nantun formation in the study area. On this basis, the lake floor fan sedimentary model of Nantun Formation in Chaganuoer depression is established. It is considered that the planar microfacies sequence is characterized by the variation of "main channel of inner fan, braided channel of middle fan, turbidite of outer fan and mud of deep lake", and that the channel systems (main channel and braided channel) are separated by obvious scale mudstones of deep lake facies. Controlled by this sedimentary model, the sublacustrine fan deposits extend far from the eastern steep slope zone to the center of the lake basin in the southern part of the study area, while the sublacustrine fan deposits gradually transit to fan delta deposits from south to north with the weakening of the influence of structural slope breaks.
According to the principle of least square method, the H-Q curve of the centrifugal pump is fitted with power function, polynomial and exponential function, and the error analysis of fitting curve is carried out by using the data of factory performance curve. The results show that the accuracy of fitting with polynomial is higher. After the fitting is completed, the centrifugal pump will have a certain deviation from the factory performance curve provided by the equipment manufacturer in actual operation. Because the number of pump operation data may be very small, the output performance curve is corrected by moving up and down from left to right. To correct the factory performance curve, the actual engineering data are used to correct the performance curve, which makes the corrected performance curve more applicable to actual production. An example analysis shows that the head is calculated to be 60 m without correction and 94 m after calibration. Assuming that a pump can provide a head of 60 m, if we use the pump scheme without correction, one pump is turned on, but in fact one pump is far from satisfactory. Therefore, the calibration of the pump's factory performance curve has a great influence on the subsequent pumping schemes.
It was proposed that the advanced⁃treatment of polymer⁃flooding produced water and realized the re⁃injection requirements. The feasibility and potential of further deep filtration treatment of wastewater containing polymer after ordinary treatment were studied by numerical simulation. The available advanced⁃filtration process pattern was established and optimized based on the distribution of oil droplets and suspended solid particles, the concentrations oil and suspended solid in filtered water, and the removal rates of oil and suspended solid. The results indicated that the advanced⁃filtration process pattern with "double graded⁃media + three graded⁃media" could further improve filtration performance depended on hydraulic and interfacial effects. The removal rates of oil and suspended solid reached 87.78% and 87.11%, respectively. The oil content and suspended solids of filtered water were controlled within 5 mg/L required for deep water treatment. This is a potential filtration process model for advanced treatment of polymer⁃containing wastewater, and also provides a basis for effectively dealing with water quality problems in tertiary oil recovery by chemical flooding in oilfields.
For the oil fields developed by the production sharing model, the existing economic limit production calculation method is not applicable. In order to solve this problem, a calculation model of the production of the economic boundary of a single well with consideration of proportion is established by using the principle of break⁃even analysis and the reservoir engineering method. The new model is used to analyze the effects of the factors such as proportion, water⁃cut and oil price on the economic limit production. Under the same water⁃cut condition, the higher the proportion, the lower the limit production. The higher the water⁃cut, the higher the economic limit production. The limit water⁃cut chart of oil field is established. The higher the proportion, the higher the oil price and the higher the limit water⁃cut. Based on the technical and economic parameters of A oilfield, the economic limit production and water⁃cut under different conditions are calculated at oil price of 70$/bbl,and corresponding adjustment measures are proposed , which guides the treatment of low⁃production wells and reduces the operating cost. That shows the model can be used to sharing development oil field to determine the economic limit production and limit water⁃cut.
Aiming at the problems of large amount of oilfield waterflooding technology, long measuring and adjusting period, low precision of measuring and measuring, and severe influence of well inclination, the mechanical stratified water injection technology is studied. The technology for the first time adopts hydraulic machinery style control, and integrates intelligent downhole monitoring, automatic tool control and other characteristics, to achieve a real⁃time monitoring, on⁃line measurement functions. The successful application of this technology in Well X6, an oil field in Bohai sea in June 2017 shows that the stratified water injection tool has reliable performance, on⁃line real⁃time measurement and adjustment, and improves the measuring and adjusting efficiency. It can be applied to acidizing operations, interwell tracer and other operations, and provides a new technical idea for stratified water injection development technology in Bohai oilfield.
