Technique using expandable backfill mix with chemical additive compound
For reliable formation segregation, PNG SC LLC offers an integrated technique of production string cementing in well bottom sections including productive and water-bearing strata, applying expandable backfill mix and chemical additive compound influencing both backfill mixtures’ rheological characteristics and cement stone strength and plastic properties. Expandable backfill mix application for productive strata shut-off has been studied for many decades, there have been written many articles and even scientific works. However, application of an integrated approach to expandable backfill mix preparation for well bottom section cementing enables to achieve much more substantial results. Casing string cementing technique using an integrated approach is intended to prevent the appearance of inter-reservoir cross-flows and oil and gas ingresses in borehole annulus at oil and gas well completion, development and operation on the fields where application of conventional materials and processing methods do not ensure reliable isolation of oil, gas and water-bearing strata. Expandable backfill mixes complete with a number of chemical agents enhance the strength of cement stone cohesion with casing string and borehole walls, they strengthen, plasticize cement stone and reduce its gas permeability. Mix expansion dynamics is chosen in a way enabling to achieve maximal expanding and adhesive characteristics while preserving cement stone integrity and strength within the entire well operation period. Backfill mix rheological properties and cement stone plasticity are adjusted at bulk blending plant using expandable cement composition processing by means of their mechanical mixing with chemical additives. Software and batch metersetof the bulk blending plant exclude mistakes in observance of the preset ingredient rated proportions.
Application of diverse methods of production casing cementing, the use of expandable backfill mixes with the required expansion and plasticity factors provide:
- Enhancement of adhesion characteristics due to a larger contact area of cement with casing and rock;
- Extension of well operation period due to segregated formations’ impermeability;
- Compaction of cement junction with string and rock disables formation fluid migration in casing annulus, which fact exerts positive influence at pressure differential between the strata, draw-downs at stimulation treatment, perforation and formation hydraulic fracturing etc.
- Essential reduction of gas permeability of both cement stone itself and of its junction with rock and casing due to application of gas isolating components in expandable backfill mixes;
- Solution of the problem of lifting cement slurry up to the wellhead - due to application of a compound of specific chemical additives possessing expandable properties in permafrost rock areas.