Low-density plugging cement paste system for well cementation of fractured reservoirs

Abstract

The invention provides a novel low-density plugging cement paste system for a fractured reservoir. The system comprises the following components in parts by weight: 100 parts of oil well cement, 10-50parts of glass micro-beads, 30-50 parts of silica micro-powder, 0-30 parts of a composite reinforcing material, 5-15 parts of a fluid loss agent, 1-2.5 parts of a dispersing agent, 3-8 parts of a retarder, 1-3 parts of fibers and 80-110 parts of water. According to the invention, the low-density plugging cement paste system for the fractured reservoir has excellent high-temperature resistance, excellent right-angle thickening performance and excellent long-term mechanical properties, can effectively enhance the stratum pressure-bearing capacity to 3.5-7.0 MPa, is expected to effectively solvethe main problems of high temperature, leakage, set cement strength decline and the like in deep fractured reservoir cementing, and has very wide application prospects.

Description

technical field [0001] The invention relates to a low-density plugging cement slurry system for cementing wells in fractured reservoirs in the technical field of cementing materials, and is especially suitable for deep buried hill reservoirs and carbonate rocks where the well depth exceeds 4000m and the bottom hole temperature exceeds 150°C. Reservoir types with well-developed fractures such as oil reservoirs. Background technique [0002] With the development of drilling and completion technology, oil and gas exploration continues to expand to new fields. At present, the exploration of complex stratigraphic reservoirs such as deep ancient buried hills and marine carbonate fractured reservoirs has become an important direction of exploration and development. This type of oil and gas reservoir has the characteristics of deep burial (generally greater than 4,000 meters), complex lithology, and developed fractures and pores. Even if the near-balanced drilling process is adopt...

AI Technical Summary

Problems solved by technology

However, the low-density cement slurry system has a long setting time and low early strength; before the low-density cement develops strength, the active formation fluid has penetrated into the cement slurry, destroying the stability of the cement slurry system

Especially when the cement density is lower than 1.30g / cm 3 When the water-cement ratio of the system increases, the water loss of the system increases, which shows that the stability of the system is poor, and the floating beads are easy to float to form water bands, which cannot achieve the purpose of sealing formation water and protecting casing, especially in buried hills and In fractured reservoirs, the burial depth is large, and the bottom hole temperature is high. The strength decline of cement stone at high temperature will cause the strength of the cement sheath to be insufficient to effectively seal the oil-water layer, causing interlayer channeling; at the same time, the system , a sharp increase in water loss, a sharp increase in the water loss of the cement slurry may cause the cement slurry to solidify in advance, and the cementing construction is safe

[0004] At present, there is no report on low-density cement slurry plugging cement slurry system suitable for the main oil layer section of fractured oil reservoir at home and abroad. It is necessary to develop a low-density cement slurry system with excellent high temperature resistance and plugging performance, stable system, low water loss and high strength to meet the sealing requirements of the main oil layer in fractured reservoirs

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