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A temperature-sensitive deformable fibrous capsule with shape memory has been developed to address the difficulties in mixing cement slurries and the slurry thickening problem caused by the oversize and excessive dosage of the fibrous materials presently in use, such as glass fiber, polypropylene fiber, sisal fiber and ceramic fiber etc. When the ambient temperature is lower than the deformation-response temperature, the particle sizes of the fibrous capsules are relatively small, therefore it is easy for the capsule particles to form high density particle packing in passages through which cement slurries are lost. When the ambient temperature reaches the deformation-response temperature, the fibrous capsules are activated and begin to expand, causing the particles packed in high densities to squeeze each other and to form high strength bridging inside the passages. The losses of the cement slurries are thus effectively brought under control. The process with which the fibrous capsules are produced can encapsulate 6 mm fibers into a 3 mm capsule, thereby increasing the effective concentrations and sizes of the fibers in loss-control cement slurries, improving the plugging performance of the cement slurries, minimizing the risks of fluid losses and ensuring the job quality of well cementing. The average fluidity of a cement slurry treated with the temperature-sensitive deformable fibrous capsules is 22 cm, and the initial consistency of the cement slurry is 25 Bc, comparable to the consistency of the pure cement slurry. Compared with cement slurries directly treated with fibrous materials, the cement slurry treated with the temperature-sensitive deformable fibrous capsules has rheology and pumpability that are significantly improved and the compressive strength of the set cement is greatly increased. The 7 d compressive strength of a set cement containing 5% temperature-sensitive deformable fibrous capsules reaches 50 MPa. The development and application of the temperature-sensitive deformable fibrous capsules help solve the difficulties encountered in cement slurry mixing and the slurry thickening problem, and are of significance to the success of high-quality well cementing operation. [ABSTRACT FROM AUTHOR]

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A new device is developed aimed at evaluating the effect of the hydration heat of the cement on the amount of the dissociated hydrate during well cementing operation. In developing this device, the contact manners of the cement slurries with the hydrate are fully considered. Using this device, hydrates at low temperature and high pressure can be generated, the cement slurry can be pumped under pressure into the wellbore while in contact with the hydrate layers, and the effect of the hydration heat of the cement slurry which is directly in contact with the hydrate layers on the formation temperature and pressure is directly measured. By calculating the gas saturation of hydrates and the amount of gas released from the dissociation of hydrates, a method of developing simulated hydrate formation is established taking into account the properties of the device, and a method is formulated for evaluating the effect of the hydration of cement on the stability of hydrate layers. In laboratory experiments, a simulated hydrate formation is constructed based on the geology of the shallower formations in south China Sea, three different cement slurries (a blank class G oil well cement slurry, a low-density cement slurry and a low-heat cement slurry) are pumped into the simulated hydrate formation. The experiment results show that in the setting process of the cement slurries, the quantities of the gas released from the hydrate by the heat from the hydration of the three kinds of cement are 0.7356, 0.1091 and 0.0649 mol/L, respectively. These results show that the low-heat cement slurry can greatly shorten the time required for the cement slurry to set. This study has provided a method of directly testing the effect of cement hydration on the hydrates in the shallower formations, and it also shows that low-heat cement should be used in cementing the hydrate formations in deep water drilling. [ABSTRACT FROM AUTHOR]

Copyright of Drilling Fluid & Completion Fluid is the property of Drilling Fluid & Completion Fluid Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Drilling Fluid & Completion Fluid is the property of Drilling Fluid & Completion Fluid Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Drilling Fluid & Completion Fluid is the property of Drilling Fluid & Completion Fluid Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The micro crack and micro annular gap are inevitable during the production of condensate gas reservoir in Shunbei oil & gas field, but the existing self-healing agent has low temperature resistance, and the evaluation method of self-healing ability is very different from the downhole working conditions. So it can not be applied to Shunbei oil & gas field. A self-healing emulsion in gas suitable for Shunbei oil & gas field is developed, with the volume expansion rate in gas reaches 30%. This agent can prepare selfhealing cement slurry with density range of 1.45-2.20 g/cm³, which is suitable for 90-180 ℃, with low modulus of elasticity <7 GPa. At the same time, a reasonable evaluation method for the self-healing ability of cement in gas is devised. Through the first and second artificial fractures making, the self-healing ability of cement paste is 100% and 95.1% respectively. At present, the selfhealing cement slurry for gas has been tested in 3 wells, and the high quality rate of cementing quality is 100%, which meets the needs of long-term sealing of HTHP gas wells in Shunbei oil & gas field. [ABSTRACT FROM AUTHOR]