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Microcracks can occur in oil well cement, which can lead to regional isolation and casing corrosion or even serious damage to the well. Self-healing cement is therefore of great interest for oil well applications. In this work, a self-healing material (called YW) was prepared by catalytic synthesis of a double-proton acid and characterised by Fourier transform infrared spectroscopy. The self-healing performance of cement with different additions of YW was evaluated in terms of permeability and compressive strength. The self-healing mechanism was analysed using pore structure analysis, scanning electron microscopy and energy dispersive spectroscopy. The results revealed that YW can significantly improve the compressive strength of cement and reduce its permeability. It can also continue to complex calcium hydroxide to generate insoluble acicular substances, so unhydrated cement particles can continue to hydrate to generate hydrated calcium silicate gel and calcium hydroxide.

The traditional fault detection method only establishes a global model and does not consider the local information of the process. At the same time, the data in the industrial process has time-varying and non-linear characteristics, limiting the prediction accuracy of fault monitoring. Therefore, fault detection and diagnosis of the method is proposed based on multi-block just-in-time-learning slow feature analysis (JITL-MBSFA). Firstly, mutual information (MI) is segmented into two sub-blocks based on normal observation data sets. Then, through just-in-time-learning (JITL) to screen the optimal data set, and based on slow feature analysis (SFA) to build a sub-model, calculate the corresponding monitoring statistics, the support vector machine (SVDD) to monitor the results of fusion. Finally, the comparative simulation experiment in the Tennessee Eastman (TE) process verified the effectiveness and superiority of the proposed method.

As a non-destructive and non-invasive technique with high stability and continuity, low-field nuclear magnetic resonance (low-field NMR) was used to characterise the initial hydration process of cement slurry systems based on grade G oil well cement, which is widely used in various cementing operations, and microfine cement, which is playing an increasingly important role as a reinforcing material, especially in the field of low-temperature cementing. The initial hydration process of the cement slurry systems was investigated using the Carr–Purcell–Meiboom–Gill (CPMG) technique. This method was used as it has the advantage over other spin echo techniques in that it allows rapid multiple accumulations of the echo train signal, which is an important issue in increasing detection sensitivity at low fields. The transverse relaxation time (T2) distribution curve and CPMG echo train of the cement slurry systems were first obtained. Then, the initial hydration process of grade G oil well cement and microfine cement was characterised by using the peak area and the value and distribution of T2. The results showed that the low-field NMR has great potential in the characterisation of the hydration process of cement-based materials.

The cement sheath may crack during oil and gas production. Due to the microcrack areas are difficult to locate and reach, the repair of microcrack can be achieved by self-healing materials. Potassi...

Based on the cement hydration theory and nucleation seeding, the nano-SiO2 and Al2O3 were introduced into the cement slurry system; then, the low-field nuclear magnetic resonance (NMR) was used to ...

Based on the low hydration heat requirement of cement slurry system used in natural gas hydrate formation and the effective utilization of industrial waste materials, the fly ash and slag were introduced into ordinary Portland cement to prepare a low hydration heat cement slurry system. During this study, the influences of fly ash and slag on the heat evaluation of cement slurry system were investigated by temperature profiles and hydration heat, which were tested by using a developed semi-adiabatic test equipment. Currently, the temperature profiles of cement slurry system were studied by the initial temperature (Ti), temperature rise (Tr), maximum temperature (Tm), and the hydration time (tm) corresponding to the maximum temperature, respectively. Moreover, the investigations of the influences of fly ash and slag on the strength property of cement stone were investigated. Then, a novel low hydration heat cement slurry system CFS1-1 used in natural gas hydrate formation was developed by the mass ratio of 2:1:1 (cement: fly ash: slag). Simultaneously, the initial hydration process of CFS1-1 was investigated by low field NMR, the rheological and thickening properties of CFS1-1 were also studied. Besides, some other application performances, such as density, fluidity, stability and consistency, were also studied. As a result, it was found that the application performances of CFS1-1 meet the cementing requirement of hydrate formation. In addition, the effective and reasonable utilization of industrial waste materials were also realized during this study.

Based on the advantages of nondestructive and noninvasive technique, high stability and continuity, currently, the low-field nuclear magnetic resonance (NMR) analyzing and testing technology (low-field NMR) has been used to characterize the initial hydration process of cement slurry system. As a kind of cement-based material, class G oil-well cement has been widely used in various cementing operations, and the basic research of class G oil-well cement has aroused wide attention. Simultaneously, microfine cement plays an increasingly important role as reinforcing material, especially in the cementing operation of low-temperature formation. Besides, the main advantage of Carr–Purcell–Meiboom–Gill (CPMG) technique with other spin echo techniques is that it allows rapid multiple accumulations of the echo train signal—an important issue in increasing the detection sensitivity at low fields. Therefore, during this study, the initial hydration process of class G oil-well cement and microfine cement was characterized by the values and distribution ranges of the time constants T2i [the attenuation of the function of the transverse magnetization 2 (t) was measured by means of CPMG pulse sequence, normalized to an initial value 2(0) = 1, and decomposed into a sum of exponential functions 2 (t) = Σ pi exp (− t/T2i) with the fractions Σ pi = 1]. As a result, it was confirmed that the low-field NMR has a great advantage in the characterization of early hydration reaction of cement-based material.

Based on the low hydration heat requirement of cement slurry system used in natural gas hydrate layer and the shortcoming of traditional methods, a novel material, namely, micro-encapsulated phase change material (MPCM-1) was synthesized and used to regulate the temperature profiles and hydration heat of the cement slurry system by a physical method. During this study, the hydration heat was absorbed by MPCM-1 when the temperature of cement slurry system beyond the melting point of the phase change material (PCM), and then the hydration heat was released by the MPCM-1 when the temperature of cement slurry system drops below the crystallization point of PCM. The MPCM-1 containing low melting paraffin wax with urea formaldehyde resin shell was prepared by the method of in situ polymerization. At first, the structure of MPCM-1 was obtained by infrared spectrum analysis (FT-IR). Secondly, the phase change properties of MPCM-1 were measured by using a differential scanning calorimeter (DSC). As a result, it was shown that the melting point and heat of fusion of MPCM-1 is 23.09 °C and −97.49 J/g, respectively. Moreover, the thermal stability of MPCM-1 was obtained by using a synchronous thermal analyzer. Simultaneously, the surface morphology, particle size and distribution of MPCM-1 were also measured by using a scanning electronic microscope (SEM) and Laser particle size analyzer. Then, the MPCM-1 was introduced into the ordinary Portland cement slurry system to prepare a low hydration heat cement slurry system, the heat evaluation of cement slurry system were investigated by using a developed semi-adiabatic test equipment. The controlling effects of MPCM-1 on the heat evaluation of cement slurry system were investigated by the temperature profiles and hydration heat. Particularly, the temperature profiles were characterized by the initial temperature (Tin), temperature rise (Tr), maximum temperature (Tmax), and the hydration time (tmax) corresponding to the maximum temperature (Tmax), respectively. Besides, the effects of MPCM-1 on the mechanical strength of cement slurry system were also studied. As a result, it was shown that the use of the synthesized MPCM-1 reduced the Tr and Tmax of cement slurry system, it was also confirmed that the cement slurry system prepared by the synthesized MPCM-1 presented excellent mechanical properties.

Based on the molecular structure requirement of the synthesized polymer resistant to higher temperature and the lower cost demand of water-based drilling fluid system, a kind of synthesized polymer Poly(SSS/AM/AMPS) was prepared by using 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AM) and sodium p-styrenesulfonate (SSS) through inverse emulsion polymerization. Firstly, the molecular structure, molecular weight distribution and thermal stability were studied. Secondly, the Poly(SSS/AM/AMPS) was introduced into water-based drilling fluid system. As a result, when adding amount is 1.2 wt%, it was found that the water drilling fluids is more fitted to the Herschel - Bulkley flow model. Besides, before and after thermal aging test, the FLAPI of drilling fluid system is 9.20 and 9.40 mL, respectively. Moreover, it was shown that the higher temperature resistance of drilling fluid system was also improved, and the operation cost was decreased. Furthermore, the results of adsorption analysis, zeta potential method and morphology analysis shows that Poly(SSS/AM/AMPS) improves the filtration properties of drilling fluid system by absorption and physical plugging.

Novel comb-shaped trimeric nonionic surfactant was synthesized with diethylenetriamine and organic acids, and then the chemical structure of the trimeric nonionic surfactant was characterized by Fourier transform infrared (FTIR) and elemental analysis. The interfacial film strength and critical micelle concentration (CMC) were measured by interface tension method. The emulsification properties was obtained by emulsification rate experiment and low field nuclear magnetic analysis, and the thermal stability of emulsions were also obtained by microscopic analysis and low field nuclear magnetic analysis. And then the comb-shaped trimeric nonionic surfactant showed an excellent emulsification effect with 2.5 wt% adding amount in oil based drilling fluid. The performance of drilling fluids with various emulsifier adding amounts were investigated by rheological measurements, thermal stability analysis and filtration experiment. These results shows that the comb-shaped trimeric nonionic surfactant as an emulsifier improved the application performance of oil based drilling fluids, it was also found that the results in our work maybe provided a new research ideas about structure-performance relationships for the new trimeric nonionic surfactant.

Using Zeta potential, adsorption capacity, contact angle, molecular dynamics simulation of the adsorption of sodium carbonate on the surface of calcium carbonate (CaCO3), we outline the mechanism of the in situ surface activation of CaCO3 nanoparticles via interaction with sodium stearate and a double phase inversion of emulsions. The CaCO3 nanoparticles can be activated in situ surface activation by adsorbing sodium stearate to become an effective emulsifier. After adding different initial concentrations of sodium stearate to CaCO3 nanoparticles dispersion, a monolayer or bilayer of sodium stearate will form at the surface of CaCO3 nanoparticles. There exists an inversion of CaCO3 nanoparticles from hydrophilicity to hydrophobicity and subsequently back to hydrophilicity. A double phase inversion, O/W (1) → W/O → O/W (2), is thus achieved by the synergistic effect of CaCO3 nanoparticles and different initial concentrations of sodium stearate.

In this paper, low-field nuclear magnetic resonance (NMR) was used to research the stability of water-in-oil emulsion droplet in oil-based drilling fluids. First, the transverse relaxation time T2 of white oil and pure water are obtained by the CMPG pulse sequence, and then, a further qualitative analysis about the T2 distribution curve of water-in-oil emulsion is conducted by introducing the relaxation reagent MnCl2·4H2O; the relaxation peak which located in between 10 and 1000 ms is corresponding to the overlapping peaks of moderate-movable free water and white oil, which is defined as emulsion relaxation peak; the relaxation peak which located at between 1000 and 10,000 ms is corresponding to the high-degree-movable free water. Thus, in this paper, we choose the relaxation peak area ratio and relaxation peak spacing as quantitative indicators to study the influences of relaxation reagent, oil-to-water ratio and aging temperature on the transverse relaxation time T2 distribution curve of emulsion. In addition, low-field NMR was also used to test the relative oil content in oil-based drilling fluids emulsion. The results shows that the low-field NMR is an efficient, fast, and accurate analysis and test technology to reflect the stability of oil-based drilling fluids emulsion droplet, while at the same time, it can also be used to test the relative oil content in oil-based drilling fluids emulsion or crude oil efficiently and accurately.

In this paper, a new kind of oil cement retarder is prepared by aqueous solution polymerization using acrylamide (AM), 2-methyl-2-acrylic amide propyl sulfonic acid (AMPS) and maleic anhydride (MA) as monomers, and then the polymer PAAM (the acronym of polymer is synthesized by AM, AMPS and MA) was characterized by Fourier transform infrared spectroscopy, the paper also introduced the field performance of this new kind of oil well cement retarder PAAM. Additionally, low field nuclear magnetic resonance (LF-NMR) test technology is employed to test the transverse relaxation time T2 distribution of cement slurry in hydration process, the pure cement slurry C and the cement slurry CHN-1 mixed with polymer PAAM were used as the research object. Finally, combined with the scanning electron microscope (SEM), a further exploration about the retarding mechanism of polymer PAAM was conducted, which shows that mainly reflected in the adsorption, precipitation and complexation effect.

In the oil exploitation process, the conversion from water-in-oil emulsion to oil-in-water emulsion is usually needed for a better cementing quality after using the water-in-oil emulsion drilling fluid. Due to the advantages of both oil-external properties for drilling and water-external characteristics for completion, the reversible emulsion drilling fluids are being used in drilling industry. The researches about phase inversion of emulsion induced by nanoparticles and amphiphilic compounds are also being conducted. Using white oil–water system, emulsion stabilized by CaCO3 nanoparticles and sodium stearate was investigated. The raw CaCO3 nanoparticles were activated in situ by interaction with sodium stearate in aqueous solution. The mechanism of the in situ surface activation was accessed by means of emulsion characterization, adsorption measurement and contact angle. The results show that raw CaCO3 nanoparticles can be activated in situ as emulsifiers by interaction with sodium stearate. With the monolayer and bilayer formed at the CaCO3 nanoparticles–water surface by absorption of different concentrations of sodium stearate, the wettability of the particles will transform from hydrophilicity to hydrophobicity and then back to hydrophilicity. The change of wettability may induce a phase inversion of emulsions from oil-in-water O/W (1) to water-in-oil W/O and re-invert to oil-in-water O/W (2). CaCO3 nanoparticles can thus be used as good stabilizers of both O/W and W/O emulsions once activated in situ by mixing with suitable amounts of sodium stearate.

The lower heat of hydration and temperature rise of slurry were required for hydrates formation cementing, the traditional experimental methods often result in a great reducing in the application performances. Therefore, the organic and inorganic composites were applied to develop a novel cement slurry, which could be used for hydrates layer in deep-water region or permafrost. Firstly, the micro-encapsulated phase change materials (MPCM) containing low melting point paraffin wax with urea formaldehyde resin shell was prepared by the method of in situ polymerization, the basic performances of MPCM, such as chemical structure, encapsulation rate and phase change properties, were studied. Secondly, the slag and fly ash were firstly added into class G oil well cement to reduced the heat of hydration and temperature profiles through chemical means. Then, the MPCM was added and applied to control the heat evolution and regulate temperature profiles, and a novel micro-encapsulated phase change materials with low melting point slurry was provided. Based on above study, a low temperature profiles and hydration heat cement slurry was developed by using organic and inorganic composites, and the developed slurry could be well applied in deep-water region or permafrost cementing to prevent the destabilization of hydrates.

During the cementing process of natural gas hydrate (NGH) layer, the hydration heat of cement slurry can easily cause decomposition of NGH which leads to cementing risk. A thermal control material of phase change micro-capsule (PCM-1) with paraffin as the core material and urea-formaldehyde resin as the wall material was successfully synthesized, and then a low hydration heat cement slurry was prepared by using PCM-1. The basic performances of PCM-1 were characterized by using DSC, FTIR, SEM and TG, and the results show that the performances meet designed requirements. Then, the PCM-1 was introduced into cement slurry system, and the hydration heat (Q) and hydration temperature rise (Tr) were measured by using the self-developed semi-adiabatic test equipment. As a result, it was confirmed that the Q and the Tr decrease with the increase of PCM-1 content. The Tr of cement slurry CP15% was 25.4 °C, lower than that of cement slurry CB. Meanwhile, compared with cement slurry CB, at 24 and 48 h hydration heat of cement slurry CP15% were decreased by 7.68 × 104 and 7.28 × 104 J, respectively. Therefore, the decomposition of NGH was avoided attribute to the smaller Q of cement slurry, and the cementing operation risk in deep water was reduced.

In this paper, Low Field nuclear magnetic resonance (NMR) was used to study the effects of synthesized retarder HN (which is the symbol of synthesized retarder) on the water states’ variation in the hydration process of cement slurry specimens. Retarder HN was prepared by acrylamide, 2-acrylamido-2-methyl propane sulfonic acid, and maleic anhydride, and the chemical structure was confirmed by Fourier-transform infrared spectroscopy and elemental analysis. Then, Low Field NMR was employed to test the transverse relaxation time distribution of the cement slurry specimens and cement stones. Here, the cement slurry and cement stone specimens have different cement-to-water ratio, retarder HN adding amount and curing age. The Low Field NMR can be used to characterize the water states and study the water states, variation in the cement slurry hydration process. Of course, the pore distribution development of cement stones was also studied in our research. Additionally, the phase analysis of cement hydration products was produced by an X-ray diffractometer, and the results showed that the retarder HN has a significant effect on the cement hydration process but without any effect on final cement hydration products.