Abstract: A well cementing method is described for improving cementing quality by controlling the hydration heat of cement slurry. By controlling the degree and/or rate of hydration heat release from cement slurry, the method improves the hydration heat release during formation of cement with curing of cement slurry, improves the binding quality between the cement and the interfaces, and in turn improves the cementing quality at the open hole section and/or the overlap section. The cementing method improves cementing quality of oil and gas wells and reduces the risk of annular pressure.

Abstract: A high-strength Portland cement slurry for ultra-high-temperature cementing, a preparation method therefor and an application thereof. In parts by weight, the composition of the cement slurry comprises: 100 parts of Portland cement, 4-6 parts of a high temperature anti-cracking material, 80-105 parts of a high-temperature reinforcing material, 70-78 parts of water, 0.5-1.5 parts of a dispersant, 1-3 parts of a fluid loss reducer, 0.5-2.5 parts of a retarder and 0.2-0.5 parts of a defoamer; the high-temperature reinforcing material is a combination of acid-washed quartz sand, metakaolin and aluminum sulfate, a combination of acid-washed quartz sand, metakaolin, feldspar and sodium sulfate, or a combination of acid-washed quartz sand, metakaolin, feldspar and calcium nitrite. The cement slurry has good settling stability, rapid strength development in low temperatures, high compressive strength of cement stone at a high temperature of 600° C.

Abstract: A well cementing method is described for improving cementing quality by controlling the hydration heat of cement slurry. By controlling the degree and/or rate of hydration heat release from cement slurry, the method improves the hydration heat release during formation of cement with curing of cement slurry, improves the binding quality between the cement and the interfaces, and in turn improves the cementing quality at the open hole section and/or the overlap section. The cementing method improves cementing quality of oil and gas wells and reduces the risk of annular pressure.

Abstract: A bicycle sprocket assembly includes a sprocket element and a chain protector. The sprocket element has a plurality of teeth disposed on an outer periphery about a center rotation axis and at least one first attachment element. The chain protector includes a protecting portion and an attachment portion disposed radially inwardly of the protecting portion. The attachment portion has at least one second attachment element that mates with the first attachment element in response to relative rotational movement between the sprocket element and the chain protector.

Abstract: A bicycle sprocket assembly includes a sprocket element and a chain protector. The sprocket element has a plurality of teeth disposed on an outer periphery about a center rotation axis and at least one first attachment element. The chain protector includes a protecting portion and an attachment portion disposed radially inwardly of the protecting portion. The attachment portion has at least one second attachment element that mates with the first attachment element in response to relative rotational movement between the sprocket element and the chain protector.