PREDICTION OF PENETRATION RATE OF DRILLING BY USING THE ROCK ENGINEERING SYSTEM APPROACH, CASE STUDY: A WELL IN THE AZADEGAN OILFIELD

Abstract

One of the criteria in the operational efficiency of drilling is the rate of penetration of the drill bit. Numerous factors affect the rate of penetration. Identification of the effective factors on rate of penetration may lead to a more accurate assessment of drilling time, and as a result, the controlling of operational costs. The concurrent effect of the entire influential factors as well as the differing significance of each of them on the rate of penetration makes the study and optimization of drilling operations much more complicated and difficult. Using the rock engineering systems (RES), the impact of effective operational and geomechanical factors on the rate of penetration has been assessed in this article and a model has been proposed for the prediction of the rate of penetration. Data from one of the wells within the Azadegan oilfield have been used in order to study the impact of effective factors on the rate of penetration. To this end, the effective factors on rate of penetration are initially identified and then an index called “the rate of penetration index (ROPi)” is proposed through the application of the rock engineering systems approach. This index has been calculated at four different depths along the aforementioned well. The results suggested the compliance of penetration rate predictions with field observations. Moreover, porosity and uniaxial compressive strength are the most effective factors on the rate of penetration whereas the weight of drilling fluid has the smallest impact. Finally, a classification for the penetration rate index is presented.

Alternate abstract:

S obzirom na to da su čimbenici koji izravno utječu na troškove izrade bušotina, vrijeme i operativna učinkovitost imaju veliku važnost tijekom bušenja. Jedan od kriterija operativne učinkovitosti bušenja jest mehanička brzina bušenja (engl. rate of penetration, ROP). Velik broj čimbenika utječe na mehaničku brzinu bušenja. Njihova identifikacija omogućuje točnu procjenu vremena bušenja, a time i kontrolu operativnih troškova. S obzirom na istodobno djelovanje navedenih čimbenika, kao i specifičnosti njihova pojedinačnog djelovanja na ROP, analize i optimizacija operacija bušenja vrlo su složene i teške. U ovome je radu vrednovan utjecaj operativnih i geomehaničkih čimbenika na ROP korištenjem stijensko-inženjerske metode (engl. rock engineering system, RES), temeljem čega je predložen model predviđanja mehaničke brzine bušenja. Podatci korišteni u radu dobiveni su iz jedne bušotine s naftnoga polja Azadegan (Iran). Do sada su početno utvrđeni čimbenici koji utječu na ROP te je, korištenjem RES metode, predložen tzv. indeks ROP (ROPi). Navedeni je indeks za ranije spomenutu bušotinu izračunan za četiri različite dubine. Dobiveni rezultati upućuju na poklapanje predviđene brzine bušenja i stvarnih terenskih podataka. Također, rezultati su pokazali da na mehaničku brzinu bušenja najveći utjecaj imaju šupljikavost i jednoosna tlačna čvrstoća, dok gustoća isplake ima najmanji utjecaj. U radu je također prikazana klasifikacija indeksa ROP.