Patent ID: 6155357
Filing Date: 2000-12-05
Classification: E21B

Abstract:
A method of optimizing bit rate of penetration while drilling, which comprises the steps of:collecting bit rate of penetration and weight on bit data at selected times during drilling;averaging collected bit rates of penetration and weights on bit over selected time intervals to obtain an average bit rate of penetration BIT.sub.-- ROP(t) and an average weight on bit BIT.sub.-- WT(t) for each time interval t;lagging said average bit rates of penetration to obtain a first lagged bit rate of penetration BIT.sub.-- ROP(t-1) for each time interval (t-1) and a second lagged bit rate of penetration BIT.sub.-- ROP(t-2) for each time interval (t-2);performing a multiple linear regression with average bit rate of penetration BIT.sub.-- ROP(t) as the response variable and first lagged bit rate of penetration BIT.sub.-- ROP(t-1), second lagged bit rate of penetration BIT.sub.-- ROP(t-2), and average weight on bit BIT.sub.-- WT(t) as the explanatory variables over a selected time period while drilling, to obtain a mathematical model of the drilling environment during said selected time period, said mathematical model being an equation of the form BIT.sub.-- ROP(t)=.alpha.+.beta..sub.1 BIT.sub.-- ROP(t-1)+.beta..sub.2 BIT.sub.-- ROP(t-2)+.beta..sub.3 BIT.sub.-- WT(t); and,using said mathematical model to select a weight on bit to achieve a desired bit rate penetration.