Perm Polytechnic scientists have developed a grouting solution for wells that restores its integrity
To increase the service life of oil wells, they are cemented using cement slurries. This is a combination of special modifying substances and materials based on water and Portland cement. Over time, hardening, they strengthen the casing in the rock, disconnect productive horizons and isolate them from aquifers, and also prevent the collapse of the well walls. The solution may contain various additives that affect its structural and mechanical properties. But so far there is no composition that would ideally meet all the requirements. Scientists at Perm Polytechnic University have developed a cement slurry capable of self-restoring its integrity when microgaps and cracks appear. The composition is characterized by improved indicators of basic technological properties and ensures tight contact of the cement stone with the casing and the well wall.
Issued for development patent (No. 2825932). The study was carried out within the framework of the Priority 2030 strategic academic leadership program.
A casing is a structure made of pipes screwed together, which is placed in the trunk of a drilled well to strengthen and prevent rock shedding. After the casing is lowered, the process of cementing it with cement slurry occurs. It must completely, without voids, fill the space between the casing and the wellbore wall throughout the entire cementing interval.
Cement compositions for fastening wells after curing are susceptible to various impacts caused by temperature fluctuations, mechanical loads, and exposure to corrosive and hydrogen sulfide aggression. They also do not always ensure close contact of the cement stone with the rocks and the walls of the well.
Perm Polytechnic scientists have developed a unique composition of cement slurry that can self-restore its integrity after destruction due to the impact of dynamic loads on the well support (pressure testing, perforation, hydraulic fracturing, etc.), restoring the tightness of the annulus.
– The resulting cement stone of our solution has the ability to linearly expand, which ensures its tight contact with the casing and the well wall. It also restores its integrity if microgaps and cracks form in it upon contact with formation water. The use of the proposed cement mortar minimizes the need for expensive repair and insulation work, while the properties of cement mortar-stone are technologically applicable for various mining and geological conditions, – shared Doctor of Technical Sciences, Head of the Department of Oil and Gas Technologies PNRPU Sergey Chernyshov.
The solution offered by polytechnics is distinguished by the fact that in addition to Portland cement cement and basic modifying reagents, its base additionally contains a complex mineral additive of nanoaluminum oxide, talc, calcium hydroxide, gypsum hemihydrate and other impurities. It is this that ensures the restoration of cement stone after various violations.
– The composition includes a synthetic polymer based on polyacrylamide, which reduces the processes of water separation and loss of water, and a defoamer based on an organosilicon polymer, which reduces foaming. Adding a plasticizing additive based on a polycarboxylate copolymer allows you to obtain the necessary mobility of the solution, and an expanding additive increases the density of contact between the cement stone and the casing and rock, – adds Vadim Derendyaev, assistant at the Department of Oil and Gas Technologies of PNIPU.
– The self-healing process occurs as follows: particles of the mineral additive react with formation water entering a crack or microgap. They interact with it and form additional new formations in the form of insoluble structures that fill the crack and block the flow of water – explains Leading Engineer of the Detailed Design Development Department of the PermNIPIneft Branch of LUKOIL-Engineering LLC in Perm Mikhail Karmaenkov.
Compared to the analogue, the developed composition of polytechnics is characterized by improved values of indicators of basic technological properties: higher mobility, increased bending strength and, most importantly, the ability to self-heal. In field conditions, such properties will make it possible to obtain high-quality sealed support for the casing in the wellbore due to the formation of a durable cement stone capable of restoring integrity in the event of its damage.
