History of development
In 2006, the staff of the Ufa State Petroleum Technological University (USPTU) developed the first equipment prototype.
A number of bench tests was carried out, in which a series of canals, several meters long each, were drilled.
Composition of the first prototype
1 – perfobur body, 2 – whipstock, 3 – power section of the downhole screw motor, 4- centering spindle, 5 – bit, 6 – perforation tunnel, 7 – manmade cement-sand block, 8 – reservoir, 9 –screw (loader) drive, 10 – drive screw, 11 – low-pressure pipeline to drain drilling fluid, 12 – high-pressure hose, 13 – 1.3 PT-50D2 pump, 14 – compensator of pressure fluctuations, 15 – control-gauging instruments, 16 – hydraulic loader, 17 – РСТ-16М flowmeter
At the end of test cycle, the array was disassembled. An assembly wear analysis showed that all assemblies were operable and had a slight wear corresponding to the design indices. A number of decisions were taken on the enhancement of individual units to increase performance and reliability.
In 2010, a group of scientists proceeded with the experimental works on wells. In a well of the Chermasansk field, the first drilling assembly with a D-43 single-section engine was operationally tested. It was run in hole by 1,421 m in a 146 mm casing column. The first generation of "Perfobur" was not yet capable of independently cutting a window in the casing column. Therefore, a multipurpose cutting device UVU-146 was used. A section of casing column was cut in several stages: gauging a casing string, geophysical well logging, running in hole an UVU array and column milling, checking the availability of a cut "window" using GIS, installing a cement bridge in the interval of column milling, determining bridgehead and bridge underdrilling.
The well was washed, and transition to drilling fluid was made. After preparatory activities, Perfobur was preassembled on the surface. A downhole drilling motor, circulating sub, and pilot hydraulic holder were tested on industrial water at a pressure of up to 9 MPa.
When running into the well, the Perfobur was sequentially assembled from separate sections. Its overall length in transport position with the shank nozzles made 46.5 m. Running down the bottom hole assembly and drilling were carried out on the NKT-73 pipes.
According to the results of the cycle of bench and field tests of the first-generation array, it was proved that the "Perfobur" system concept had been chosen correctly. The design data agreed with the actual data. Having summarized the obtained experimental data, the team embarked on the development of a second-generation system that took into account the experience gained. It was suggested to introduce the new assembly materials and more advanced engineering solutions.
The second-generation array underwent a number of bench tests in Ufa, and later it was tested in one of the Orenburg fields. The main purpose of the field tests still was to identify the most optimal mode of drilling, select empirical coefficients of a mathematical model, and search for the ways of further reliability optimization.
A more powerful engine was applied, and an optimal kit of drilling bits was chosen. The working pressure while drilling made 6-7 MPa, which was fully in line with the design characteristics and actual data of bench tests. It was decided to use an electrically driven model of triplex pump as a pumping unit.
All completed field tests were intended to determine efficiency of the drilling assembly, to identify an optimal mode of operation (pump flow, weight on bit, pressure, vibration level, and of penetration).
In 2015, an improved version of the third-generation array was designed to complete the test cycle and start the commercial introduction.