New Downhole Instrument with Improved Vibration Stability is Developed in Samara

September 7, 2012

An engineer from Samara, applied for a Patent on downhole instrument upgrading to improve vibration stability and operational characteristics. The electronic module design was optimised on the basis of tests under severe downhole vibrations with the aim of development of a unified telemetry system having high performance characteristics.

Significant difference in the operating conditions of the instruments included in the telemetry system installed in the bottomhole assembly (BHA) and their analogs intended for open hole logging is mostly related to the incommensurable level of vibration and impact load caused by the rock cutting tool in the course of drilling. The second key distinctive factor is the requirement on minimization of the outer dimensions (diameter in the first place) of instruments to reduce hydraulic resistance to the drilling mud flow and preservation of strength of the drill string in which the instrumentation is placed.
When designing a unified downhole instrument for the extended line of telemetry system standard sizes (conventional outer diameter of case elements ranging from 89 mm to 240 mm) engineer focused the effort on upgrading of the printed-circuit board chassis in order to improve their shock-absorbing capabilities and reduce the outer diameter with maximal use of the internal volume for placement of electronic components.

The work resulted in a technical solution shown in Fig.1; invention application for this solution was submitted and registered under No 2012127553.
The patent-pending technical solution under discussion differs essentially from the opposable analogs and eliminates or neutralizes most of their demerits by fabrication of chassis 1as a U-shaped one-piece construction of a flat parent sheet using a highly productive method of rolling.

An aluminum alloy strip 0.5...0.7 mm thick and of the required length (1.5...3 m) can be used as a blank for chassis 1. Aluminum alloys are easily deformed; they are non-magnetic and have high thermal conductivity.
Fabrication of chassis 1 in the claimed technical solution from a flat parent sheet enables the following:

- Reduce the total mass of the structure, its cost and vibration load, and also requirements to the fabrication precision due to flexibility of the open section;
- Move walls of location plates in chassis 1 away from the areas of soldering of the electronic components to plates 3;
- Make maximum use of the internal volume of the electronic module for placement of downhole instruments;
- Use electronic printed-circuit boards 3 with double-sided assembly of components;
- Place any through-line cables in one-piece chassis 1 prior to fastening of plates 3; thus the number of connections is reduced, low-current circuits of plates 3 are unloaded and their heat load is decreased;
- Reduce the diameter of the electronic module to extend the operational capabilities.

The declared technical solution differs significantly from the analogs, has significant advantages in the assembly arrangement, cost and dimension parameters, operational functionality and repairability, claims Sinitsa.

Read more - in “Oil&Gas Eurasia”, #10, 2012