Prehistory

The development of an electric downhole motor (EDM) is based on the idea of using electric energy as a more effective power for drilling operations. This kind of energy has the following advantages:

• It is cheap and convenient for long-distance transmission.

• It is easily transformed into other kinds of energy with high efficiency, allowing the use of automatic technologies and remote control.

• It maintains constant power by increasing the voltage to compensate for power losses in transmission lines.

All these reasons allow the development of highly effective DHMs for driving drillbits and automating the drilling process.

During the last 100 years, experts from the United States, Germany, France, Austria/Hungary, Romania, and Russia have tried to develop drilling machines with electric motors. The first efficient EDM for deep drilling was developed in the U.S.S.R. between 1937 and 1940. The desire to develop these motors was driven by the numerous advantages of the electric motor:

• power transmitted to the bit was high, constant, and independent of fluid flow conditions

• bit performance and rock destruction at the well bottom were controlled from the surface

• properties of the penetrated rock were conveyed by bit performance

Naturally, these advantages were accompanied by additional technical problems related to directing two parallel flows of energy to the bottom for bit rotation and bottomhole cleaning.

The first electrodrill consisted of a 3-phase, 4-pole motor with a capacity of 70 kW, a planetary gear that reduced rotation speed from 1450 to...