A downhole-started self-locking casing centralizer

Abstract

The invention relates to a downhole-started self-locking casing centralizer, comprising a connecting part (1) and a connecting part (2) on both ends, a central supporting part being arranged between the connecting part (1) and the connecting part (2), and characterized in that the central supporting part comprises a hollow coupler, and at least three N-stage piston self-locking support devices extending by stages under pressure are evenly distributed along the circumference of the coupler, N≧2. The invention has the following advantages: 1. a threaded integral structure is adopted; 2. a downhole-started self-locking support structure is adopted; and 3. a circular arc support cap helps ensure large support force and reduce damage to borehole walls.

Description

FIELD OF THE INVENTION[0001]The invention relates to a centralizer capable of centrally fixing a casing in a borehole.DESCRIPTION OF THE RELATED ART[0002]With the continuous development of the oil industry and the pursuit of productivity efficiency of high oil and gas reservoirs, the requirements for cementing quality are higher and higher, and the casing centrality in boreholes is one of the decisive factors for the quality of oil and gas well cementing. Therefore, how to accurately learn about the centralization of a casing string in a well, and how to improve the displacement efficiency in the cementing process are currently an urgent problem to be solved in oil fields. In the cementing process, the cementing quality is decided by the displacement efficiency of cementing, and the casing centrality in boreholes is an important factor affecting the displacement efficiency of cementing. Poor centrality easily results in wide edges and narrow edges. Therefore, during displacement of ...

AI Technical Summary

Benefits of technology

The patent describes a new design for a centralizer used in oil and gas wells that solves problems with existing centralizers. The new centralizer is designed to be started downhole, which means it can be used in irregular boreholes without being affected by friction. The centralizer has a high starting force and a low leakage resistance, making it more reliable and practical. The design also includes a circular arc support cap that ensures a large supporting force and reduces damage to the borehole walls. Overall, the new centralizer solves the technical problem of providing a reliable and practical centralizer for oil and gas wells.

Problems solved by technology

Poor centrality easily results in wide edges and narrow edges.

Therefore, during displacement of drilling fluid by cement slurry, cement slurry easily clings on wide edges and flows back, but drilling fluid of narrow edges cannot be displaced or fully displaced, affecting the cementing quality.

Existing conventional centralizers are basically divided into two categories: one is elastic centralizers, and the other is rigid centralizers, the elastic centralizers are designed according to the principle of springs, have advantages of large force, simple manufacturing process and low price, but have disadvantages of generating large running force during use, severely damaging borehole walls, and affecting normal casing running.

The rigid centralizers have disadvantages of high requirements for boreholes so that any undergauged interval cannot exist.

In addition, the rigid centralizers will increase the string rigidity, resulting in difficulty in casing running, and the consumption of rigid centralizers is limited due to high manufacturing cost, complicated manufacturing process and unstable reliability.

Although the centralizer has centralizing effect in borehole by sufficient restoring force generated by a bow spring leaf opened by differential pressure, the starting pressure thereof is difficult to control, and the maximum starting force is large, thus the centralizer is rarely used.

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