Article is devoted to creation of new compositions of process solutions for lining of directional wells at high temperatures. Developed compositions provide high durability characteristics of cement stone. It is shown that with an increase in packing density of cementing slurry components durability characteristics increase and porosity and permeability of cement stone decrease, whereas an increase in temperature and pressure leads to a significant increase in compressive and bending durability, which is associated with presence of quartz in them. It has been established that introduction of special structure-forming additives to the composition of developed cementing solutions allows formation of sedimentation-resistant cement systems that can provide an increase in durability characteristics of cement stone and, in general, quality lining of directional wells. Study of rheological properties of developed cementing compositions showed that the systems have high yield strength at increased temperatures and pressures. Developed compositions of water-based spacer fluids increase the cleansing degree for both casing and rocks surfaces from mud and clay cake residues, which improves the cementing quality of oil and gas wells. Mechanism for increasing the washing ability of spacer fluids and durability characteristics of cement stone, depending on composition and properties of their constituent components, is disclosed.
In the paper, the perspectives of exploration and completion of gas hydrate fields and the drilling problems in the gas hydrates of the northwest china are studied. It has been established, that the main reasons of complications in the Muli field are the secondary hydrate formation on the walls of the well and drilling assembly and ice formation inside the set cement during the well drilling and completion in permafrost. It has been shown, that in the areas with permafrost during the drilling of the layers containing gas hydrates, temperature and pressure changes can lead to the dissociation of hydrates. At the same time, pressure increase in the annular space due to the gas release, can lead to the secondary formation of gas hydrates, drill string stuck, ceasing of drilling fluid circulation, which is the reason of serious trouble in the wellbore. The results of the research on the development of drilling fluids compositions, which lower the drilling troubles of permafrost, are presented. Comparative experiments have been conducted to evaluate the effectiveness of thermodynamic and kinetic inhibitors, which prevent the repeated hydrate formation. It has been established, that the kinetic inhibitors have the clear advantage: they have good inhibiting effects even with low amounts of additives. In the laboratory conditions, the researches have been conducted to evaluate the phase equilibrium of gas hydrates during their reaction with the water solutions, containing kinetic inhibitor PVP. A thin clay drilling mud has been developed on the water base, providing the holding of the temperature in the level of –2 °С and its effectiveness for the gas hydrate fields in the PRC has been shown. Casing effectiveness of unstable rocks during the drilling in the conditions of negative temperatures inside the well largely depends on their physical-mechanical properties, composition and the technical indicators of cement materials. The authors suggest the composition of quick-setting cements based on aluminum binding materials. It has been established, that the analyzed compositions have the ability to considerably improve the results of cementing.
The article deals with ways of rock weakening for efficiency increase of hard rocks drilling, also development of drilling fluid composition is considered. Aim of the project is to develop drilling fluid composition which increases efficiency of hard rocks destruction. Authors conducted experimental investigation of drilling fluid composition development and their main structural rheological and filter characteristics. Influence of various solutions, including developed one, on hard rocks destruction process is evaluated on introduced testing bench. Investigation results indicate that composition and characteristics of developed drilling fluid positively influence hard rocks destruction process. Implementation of clayless drilling fluid with anion-active surfactant composition additives allows boost of drilling operations performance by increase in mechanical velocity of drilling and drill meterage per bit.
The paper presents properties of the rocks according to their resistance to drilling. The effects of differential pressure on the rock drillability and changes in rocks strength depending on the depth of their occurrence and crushing conditions are examined. The interlinkage between technological processes for rock crushing at the borehole bottom and breaking stresses has been analyzed. The interlinkage between the breaking loads and deformations of rocks with account of their structural changes and rate of loading has been assessed. The relevance and applicability of identified regularities between stresses, deformations and differential pressure for solving practical tasks of efficient rock crushing in the course of drilling have been assessed. Issues of providing theoretical evidence for the rock breakage with the rock cutting tools in the bottom-hole conditions have been reviewed. It is proven that the rock destruction effect of drilling depends not only on the value of the breaking load but also on the rate of its application.
In this article were shown research results connected with development of mathematical model of cementation in high-permeability rock at drilling and repair of oil and gas wells.
It shows the experimental results connected with creating of effective compositions of technological fluids for drilling and repair of oil and gas wells.
The results of researches of properties of the new native waterswelling polymer «Petrosorb» are given. Description is given to the design of plugging-up tool for liquidation of catastrophic absorption of flushing fluid in the course of drilling of oil and gas wells.
The paper focuses on the problems of oil and gas well cementation. It has been established that the main reason why formation fluids leak behind the casing is due to poor isolation of the annulus caused by incomplete cleaning of the filter cake, which results in weak or absent adhesion between the cement and the rock. The authors demonstrate that adding polymer modifier GM-II to the spacer fluid strengthens the cement-to-rock contact by several times. Moreover, mixing spacer with cement slurry does not degrade such important properties as spreadability and consistency of the latter. The paper contains investigation results on the content of polymer spacers that improve cementation quality of oil and gas wells. Spectral infrared and X-ray analysis allowed to define the impact of phase composition and mineral structure of the system «cement stone-filter cake-formation rock» on improving leak tightness of the annulus. Electron microscopic study showed that the use of polymer spacers facilitates formation of felted net-like structures between hydrated minerals. The composition of these structures, binding cement grains and clay minerals, has been studied by means of energy dispersive X-ray microanalysis. Obtained results allow to come to the conclusion that these structures mostly consist of hydrated calcium silicate (more than 77% by mass), which agrees well with the findings of infrared and X-ray analysis. Pilot tests, performed at the Shengli oil field in China, have confirmed efficiency of developed spacer fluids.
The paper considers variants of lightweight cement compositions with additives of various substances, such as clay components, ash systems, silica additives, kerogen, gilsonite, microspheres, as well as the process of cement slurry aeration. Recommendations on the use of compositions in different conditions are presented. A decrease in the density of the solution is achieved not only due to the low density of the materials used, but also as a result of an increase in the water-cement ratio. In such conditions, it is not possible to ensure the formation of a durable and impermeable cement stone in the well, which creates high quality inter-reservoir insulation. The characteristics of the physical and mechanical properties of existing lightening additives are given, which allows determining the most rational conditions for the use of cement slurries for improvement of the well cementing quality.