Study On Microencapsulation Techniques Of Super Absorbent Polymer

Lost circulation is a severe problem which is encountered during the exploration drilling of oil or gas. Due to the lost circulation, many other complex disasters may be aroused, having disadvantage to drilling and completion. Once the lost circulation happened, not only time but also drilling fluids are wasted. Meanwhile the strata having oil or gas is also damaged. So it is very important to deal with it promptly.Super absorbent polymer (SAP) is developing very fast recent years. It can absorb a very large amount of water and expand in volume. The water absorbed can sustain high pressure. It is a good choice to add SAP to drilling fluids to seal lost circulation zones. Because of the quickly velocity of Sap's absorbing water, sometimes even 0.5h making SAP the biggest volume, the parameters of the drilling fluids are affected and conveying the SAP to the lost circulation zone is also becoming a big problem.This paper using the encapsulation technology intended to encapsulate the granules of SAP, limiting the velocity of its absorbing water, meeting the time requirements demanded when pumping it to the lost circulation zones.This paper introduce the widely used lost circulation materials, such as bridging materials, high dehydration leak stoppage materials, temporarily plugging materials, chemical plugging materials as well as inorganic gel gelation gelling leak stoppage material; The development history of micro encapsulation and its preparation methods as well as the micro capsule's release mechanism are also made exhaustive elaboration.In the paper, four methods including the oil-phase-parting method, the Wruster and he melting-dispersion-condensation method, the spray-drying process methods are introduced with emphasis. These methods were adopted to carry on the research to realize the purpose that the granular of SAP can be encapsulated by the selected wall material. The laboratory procedure and the experiment phenomena had been described in detail.By the method of water-cooling-shearing, a kind of capsule, SAP embedded in the matrix, was prepared. The tested effective content and theory effective content are compared; the difference between the two is very acceptable. The samples were scanned By SEM, showing that the laminated shape was more than granulated and there were small obvious dents in the surface. It turned out that the SAP pellets had fallen off in the preparation process from the paraffin wax matrix; the SAP pellets had been wasted to some extent.