Hole Quality: Why It Matters

Abstract

Hole Quality: Why It Matters David C-K. Chen; David C-K. Chen Sperry Sun Drilling Services Search for other works by this author on: This Site Google Scholar Tom Gaynor; Tom Gaynor Sperry Sun Drilling Services Search for other works by this author on: This Site Google Scholar Blaine Comeaux Blaine Comeaux Sperry Sun Drilling Services Search for other works by this author on: This Site Google Scholar Paper presented at the SPE International Petroleum Conference and Exhibition in Mexico, Villahermosa, Mexico, February 2002. Paper Number: SPE-74403-MS https://doi.org/10.2118/74403-MS Published: February 10 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Chen, David C-K., Gaynor, Tom, and Blaine Comeaux. "Hole Quality: Why It Matters." Paper presented at the SPE International Petroleum Conference and Exhibition in Mexico, Villahermosa, Mexico, February 2002. doi: https://doi.org/10.2118/74403-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Oil Conference and Exhibition in Mexico Search Advanced Search AbstractHole quality is generally related to the "smoothness" of the wellbore or, sometimes, to wellbore stability. This paper will demonstrate that wellbore spiraling is the primary contributor to poor hole quality and that almost every well contains some degree of spiraling unless specific actions are taken to prevent it. Hole spiraling was first studied by Lubinski et al. in the 1950's, and they described it as a "crooked hole." Although the symptoms have been well recognized in the industry, only recently has a solution been proposed and tried specifically to cure hole spiraling. To implement the concept, two new drilling systems (a steerable motor and a rotary steerable) have been developed. Field data indicate that generating a straighter, high-quality wellbore has improved almost every aspect of drilling. These improvements include lower vibration, better bit life, fewer tool failures, faster drilling, better hole cleaning, lower torque and drag, better logging tool response, and better casing and cement jobs. Several case studies will be discussed to demonstrate the positive economic impact of producing a high-quality wellbore.IntroductionHole quality can have a profound effect on the total well construction time and cost and sometimes even determine the success of drilling a well. The importance of good borehole quality increases as extended-reach and offshore wells become more common, as they have in recent years.1,2 While some hole problems are a function of wellbore stability and must be addressed with proper mud weight, others arise as a result of poor wellbore geometry. For example, how accurately does the borehole itself follow the surveyed path? Does it follow a more or less helical path around the centerline of the planned well trajectory like a spiral? Poor wellbore geometry is an area that is often overlooked, but it is important that the following questions be addressed: Is hole spiraling prevalent? And, if it is, why haven't we known it?Hole spiraling is not easy to detect because MWD surveys are usually at least 30 ft apart. Because the collars will lie on the low side of the wellbore, the survey data would show very little trajectory variation. However, a sinusoidal form of borehole can be clearly seen by a wireline imaging log (see Fig. 1) or the formation evaluation logging tool data (see Fig. 2). Nieto et al.3 report that it is quite common to see borehole-induced "sinusoidal" noise on logging tools, especially those relying on contact or proximity to the wellbore wall.Some pieces of data would indicate that spiraling is prevalent in many wells. One is a study4 that showed that wells drilled with a new steerable drilling system produced friction factors significantly lower than conventional steerable systems. In some cases the friction factors in open hole and in casing were the same. The authors are not aware of any wells ever drilled that have achieved friction factors as low as these are. This new steerable drilling system employs extended-gauge bits and specially designed mud motors with pin-down connections. This system is run according to proprietary methods to ensure consistent results over many wells. The system is designed to eliminate spiraling, and there is powerful evidence that it does. The fact that low friction factors are unique to wells drilled using this system suggests that most wells drilled conventionally are spiraled to some degree.Another indication that wells are spiraled in general is the fact that a drill-string is a long slender rod with a bit on the end. Although many directional assemblies have some stabilization that tends to keep the bit closer to center, this stabilization is usually several feet behind the bit, allowing it to wander off center. By comparison, a standard drill bit made for drilling wood or metal has several multiples of the diameter worth of non-cutting gauge protection in the form of helical flutes. For example, a 1/2-in. bit has roughly 3–4 inches of "full-gauge" fluting. Keywords: high-quality wellbore, gaynor, spe 74403, upstream oil & gas, lubinski, diameter, drilling operation, hole quality, steerable system, torque Subjects: Drilling Operations This content is only available via PDF. 2002. Society of Petroleum Engineers You can access this article if you purchase or spend a download.