New blocking compounds (crosslinkers) required for efficient operation of Kovykta gas condensate field have already passed pilot tests. Their introduction into production will make it possible to avoid problems when drilling wells, which arise due to the uncontrolled flow of brine. Salty groundwater disrupts circulation of drilling fluids, which leads to their absorption into the formation. Elimination of complications takes a lot of time and leads to decrease of production profitability.
It is well known that the Kovykta field along with the Chayanda field are the resource base for supplies of the Russian blue fuel to China. Against the background of artificial decrease of demand on the part of European consumers, this field after the construction of the Power of Siberia-2 pipeline may become the main source of profit for Gazprom, one of the biggest taxpayers in our country. But in order to provide the declared volumes, which are tentatively 50 billion cubic meters per year, it is necessary to carry out serious work on increasing the debit of the wells.
"Back in the 80s of the last century, specialists encountered a serious problem while drilling this field. It consists in violation of structural-mechanical properties of drilling and process fluids due to uncontrolled brine inflow. This necessitates additional measures to preserve the environmental safety of the region, which makes well construction more expensive," says Dmitry Sidorkin, director of the Arctic Research Center at St. Petersburg Mining University.
He specifies that highly productive porosity horizons alternate with zones of abnormally high formation pressures. For this reason, most of the existing technical means and technological solutions aimed at combating complications are ineffective.
"To solve this problem, we took brine samples to analyze for chemical composition and subsequent development of crosslinkers for reservoir blocking in the conditions of salt deposits. Laboratory experiments on a modified dynamic filter press cell continued for six months. Their essence was that the core was saturated with highly mineralized fluid under high pressure, and then, after determining the degree of its filtration, the blocking compound was applied there. The task was to select the optimal components for this particular field," explained Dmitry Sidorkin.
Young scientists of the university also took part in the project. For example, postgraduate student Dmitry Sidorov made the fight against seepages the subject of his dissertation. This is a real scientific work, which "substantiates the mechanisms of formation of the fixed structure of the blocking composition when interacting with brines under conditions of high pressures and temperatures."
"The Ph.D. thesis, in my opinion, should be a serious study based on the results of experiments that were carried out as part of the scientific group. This kind of practice is one of the conditions for the further career development of young scientists at the University of Mining. In our university, academic research on a particular problem without participation in laboratory research (which often substitutes for a dissertation) is done during the first year of graduate school or during the first year of postgraduate studies. Then there is more serious work," stressed Dmitry Sidorov.
Pilot tests of the developed blocking compounds on one of the wells in the Kovykta gas condensate field were conducted by his more experienced colleagues: Mikhail Dvoinikov, scientific supervisor of the Arktika Center, and Evgeny Kambulov, well construction laboratory Evgeny Kambulov. It goes without saying that the team also included representatives from Gazprom-VNIIGAZ. This is the head research organization of Russia's largest natural gas producer.
"The tests included the following stages: before pouring the blocking compound, we pumped a weighted saline polymer-clay mud into the well as a buffer fluid, and already after - the crosslinking system itself, pushing them down to the rapiferous horizon. Three hours later a spill test was conducted, which showed stabilization of circulation, without significant manifestation of brine," said Mikhail Dvoinikov.
The successful completion of this work, according to both parties, opens up significant opportunities for expanding cooperation between St. Petersburg Mining University and Gazprom in the field of well construction. But most importantly, it proves that the reorientation of pipeline methane exports from the West to the East is not only possible, but promising in terms of replenishing the Russian budget.