Drilling in the Delaware Basin with Shaped Diamond Elements Reduces Vibration and Increases Reaching Target Depth
Authors: Phillips Anthony , Rickabaugh Caleb , Gray Joel , Savage Michael , Ramsey Josh 
Published: February 2018

Lateral stability at low depth-of-cut (DOC) has been a key factor affecting the durability and performance of polycrystalline diamond compact (PDC) bits. This paper describes how Shaped Diamond Element (SDE) technology proven in the laboratory and in Delaware Basin well construction can increase stability and boost performance with 66% improved footage while drilling 40% faster. The technology enables modifications to the cutting structure that changes the PDC bit stability response, controlling lateral instabilities.

Full bit laboratory testing was used to measure a PDC bit's lateral stability during drilling. . An experimental, intentionally unstable 8.75-in. 6 blade PDC bit frame was designed as a baseline for testing, and a second bit with the same basic frame was built incorporating the SDE technology. Tests were run to examine the effect of exposure and number of shaped diamond elements on the bit's stability. The bits were tested at atmospheric pressure, in different rocks to indicate their response in soft and hard formations. The learnings from these tests were then applied to an 8.75-in. 7 bladed PDC bit for use in the Delaware basin. The SDE field test bits were equipped with in-bit sensing to confirm the benefits in operation that were observed in the laboratory test. Data from their runs are compared with offsets to quantify the benefit of the SDE technology over a number of months

During laboratory tests in a soft limestone an instability boundary line was determined at 28% lateral instability, with a higher value indicating a more unstable bit. The baseline bit started at 28% indicating instability at low depths of cut and reached 100% with increasing DOC. The SDE bit designed for early engagement remained stable through the entire test independent of depth of cut achieving a 6% instability level. To establish the design criteria to maximize the stability benefits, the bits were tested with varying number of strategically placed SDE, and varying DOC. During the field runs with this technology, the results indicated an improvement in dull conditions increasing target depth (TD) rate by 21% and increasing the distance drilled by 10%. In one particular case, comparisons of the vibration data from the in-bit sensor showed a 42% reduction in drilling dysfunctions for this given interval, on consecutive wells on the same pad. The reduction in vibration reduced cutting structure damage yielding an increase in rate of penetration (ROP) by 40% and footage by 66% over offsets.

Recognizing these dysfunctions associated with lateral instability as the most damaging to the bottom-hole assembly (BHA) it is important that they are mitigated or controlled. The drilling costs and efficiencies today are significantly important; they are the key to reduce any non-productive time (NPT). As the field data demonstrates, SDE that engage and cut the rock, can provide stability benefits that improve the bit's durability without reducing the bit's performance.