Tiankui Guo

Experimental evaluation of fracture stabilizers

Abstract To avoid the closure of once created fractures in unconsolidated sandstone reservoirs after fracturing, an optimum fracture stabilizer was selected through experimental evaluation, dosage optimization and analysis of its suitability with other commonly used fracturing fluids. A modified resin was selected as the fracture stabilizer, which can form an adhesive film with certain adhesion intensity on the surface of the proppant to fill fractures despite the slightly decreased conductivity. The conductivity, sand control effect, suitability with guanidine gum and viscoelastic surfactant fracturing fluids (VES) of fracture stabilizers with different ratios were evaluated in the experiment. The dosage of the fracture stabilizer was optimized according to conductivity results and sand control effect. After a comprehensive evaluation, fracture stabilizer of 3% to 5% mass fraction is recommended to be used with the guanidine gum fracturing fluid. The simulation experiments show that the flow conductivity of fractures could be maintained by fracture stabilizers and in the proppant processed by stabilizers the number of intrusive particles was significantly reduced.

Evaluation and Optimization of New Nanocomposite Fiber for Fracturing Technology Based on a New Equipment

The fiber has great advantages in hydraulic fracturing when considering fluid leak off and flow friction, proppant transportation and fracture damage, proppant or sand production, and fracture geometry. However, some drawbacks, such as poor chemical stability, mechanical properties, heat denaturation, and dispersivity, always emerge in oilfield cases. Accordingly, a new type of nanocomposite fiber is used to overcome these shortcomings in our research. Generally, fiber’s conventional performance, dispersivity and proppant suspension capability can be evaluated easily, but reliable evaluation and optimization of fiber applications could not be obtained by normal indoor experimental instruments. So we developed the “fracture filling model”, a specially designed instrument to evaluate the performances of fracture conductivity, proppant backflow, and sand control. All the performances of the nanocomposite fiber were evaluated, and the length and concentration of the fiber were optimized. The results have great influences on both theoretical study and field treatments of the new nanocomposite fiber.

Study on Initiation Mechanisms of Hydraulic Fracture Guided by Vertical Multi-radial Boreholes

The conventional hydraulic fracturing fails in the target oil development zone (remaining oil or gas, closed reservoir, etc.) which is not located in the azimuth of maximum horizontal in situ stress of available wellbores. The technology of directional propagation of hydraulic fracture guided by vertical multi-radial boreholes is innovatively developed. The effects of in situ stress, wellbore internal pressure and fracturing fluid percolation effect on geostress field distribution are taken into account, a mechanical model of two radial boreholes (basic research unit) is established, and the distribution and change rule of the maximum principal stress on the various parameters have been studied. The results show that as the radial borehole azimuth increases, the preferential rock tensile fracturing in the axial plane of radial boreholes becomes increasingly difficult. When the radial borehole azimuth increases to a certain extent, the maximum principal stress no longer appears in the azimuth of the radial boreholes, but will go to other orientations outside the axial plane of radial boreholes and the maximum horizontal stress orientation. Therefore, by reducing the ratio between the distance of the radial boreholes and increasing the diameter of the radial boreholes can enhance the guiding strength. In the axial plane of the radical boreholes, particularly in the radial hole wall, position closer to the radial boreholes is more prone to rock tensile destruction. Even in the case of large radial borehole azimuth, rock still preferentially ruptures in this position. The more the position is perpendicularly far from the axis of the wellbore, the lesser it will be affected by wellbore, and the lesser the tensile stress of each point. Meanwhile, at a certain depth, due to the decrease in the impact of the wellbore and the impact of the two radial boreholes increases accordingly, at the further position from the wellbore axis, the tensile fracture is the most prone to occur and it will be closer to the axial plane of the two radial boreholes. The study provides theoretical support for the technology of directional propagation of hydraulic fracture promoted by radial borehole, which is helpful for planning well-completion parameters in technology of hydraulic fracturing promoted by radial borehole.