Drilling and Drilling Fluid Technology

Drilling Technology Types

This post carries , a short write-up on the various drilling technologies which were examined by the ONGC's expert committee.

 8Turbodrilling: The ability of the Turbodrill and the impregnated bits to stay in hole, in excess of 500 hours, at temperatures in excess of 500F, makes this system a very attractive drilling application. Moreover, unlike roller cone assemblies, the impregnated bits do not have any bearing limitations or fixed cutters like PDC bits, so the risk of fishing for lost cones is removed. The ultra-high RPM (1000 RPM) delivered to the impregnated bits by the turbodrill allows the bit to cut the formation in a similar manner to a grinding wheel. Turbodrill and impregnated bits are a specialized drilling system designed for highly abrasive and high compressive strength rocks.

 --Turbodrills and impregnated drill bits have set multiple world record for endurance and penetration rates in similar directional and vertical applications drilling out the shoe-track to the target depth in a single run. The increased power delivered by the turbine, combined with the reduction in weight on bit (WOB) requirement results in superior impregnated bit durability as well as the penetration rate compared to the same bit ran on a high-speed Positive Displacement Motor.

 --A Turbodrill provides several benefits for more efficient drilling operations as well as obtaining more accurate downhole information. For example, the tool can maintain high rotational speeds for long periods, 400-600 circulating hours routinely, and more than 700 hours in single case. In fact, the turbodrill's mean time between failure (MTBF) is 2,750 hours for the entire tool fleet. The reliability and durability combined with no decrease in tool efficiency translates into improved ROP, meaning substantial cost savings to operators during drilling operations.

 8Downhole Motor: This application can achieve an ROP of approximately 20% to 30% better than the conventional drilling. In a down hole motor, a bit can rotate at about 150 RPM.

8Air Hammer Drilling: Air hammer technology is used in top and intermediate sections (non-reservoir sections) where hard formations are encountered at the surface leading to lower ROP, excessive drilling time, high bit consumption, excessive tripping time, deviation problem due to high WOB and drilling string failure.

 --To overcome these problems the use of air hammer drilling is recommended. The air hammer drilling equipment includes a hammer bit, an air compressor unit, a rotating control head, a drillstring valve and a return handling system.

 --ROP achieved by air hammer drilling is far ahead of conventional drilling. But this technology can only be applied where the compressive strength of rocks in more than 15000 Psi.

Drilling Fluid:

 Presently prevalent drilling practices in India for oil & gas exploration and exploitation we use electrical or mechanical rigs with heavy machines and a drilling fluid circulatory system.

Drilling fluid is a mixture of various chemicals which is so designed to lift all drill cuttings to the surface, keep the drilling bit cool, lubricate the string of pipes rotating in the hole.

This drilling fluid has various types of parameters for optimized drilling and successful completion of the well. Experts (who are qualified in the field of Chemistry) are required to manage the drilling fluid quality.

In the subsequent post I shall try to detail some important success tips for trouble free well drilling.