Challenges of Drilling an Ultra-Deep Well in Deepwater - Spa Prospect

Challenges of Drilling an Ultra-Deep Well in Deepwater - Spa Prospect Stephen A. Rohleder; Stephen A. Rohleder ConocoPhillips Search for other works by this author on: This Site Google Scholar W. Wayne Sanders; W. Wayne Sanders ConocoPhillips Search for other works by this author on: This Site Google Scholar Roger N. Williamson; Roger N. Williamson ConocoPhillips Search for other works by this author on: This Site Google Scholar Gary L. Faul; Gary L. Faul ConocoPhillips Search for other works by this author on: This Site Google Scholar Lynn B. Dooley Lynn B. Dooley ConocoPhillips Search for other works by this author on: This Site Google Scholar Paper presented at the SPE/IADC Drilling Conference, Amsterdam, Netherlands, February 2003. Paper Number: SPE-79810-MS https://doi.org/10.2118/79810-MS Published: February 19 2003 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Rohleder, Stephen A., Sanders, W. Wayne, Williamson, Roger N., Faul, Gary L., and Lynn B. Dooley. "Challenges of Drilling an Ultra-Deep Well in Deepwater - Spa Prospect." Paper presented at the SPE/IADC Drilling Conference, Amsterdam, Netherlands, February 2003. doi: https://doi.org/10.2118/79810-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/IADC Drilling Conference and Exhibition Search Advanced Search AbstractConoco drilled the Spa Prospect, Walker Ridge 285 #1, in the Gulf of Mexico to a depth of 29,452' MD / 29,434' TVD. The Spa Prospect was a subsalt well encountering approximately 9,981' of salt. The Transocean Deepwater Pathfinder, a dynamically positioned drillship, was utilized to drill this well in 6,654' of water. Original planned total depth for the well was 31,600' MD / 31,000' TVD. This represented one of the deepest wells ever planned in the Gulf of Mexico. All geologic objectives were reached by 29,452' and drilling operations were terminated.This paper describes the challenges involved with planning the well, documents the execution, and concludes with lessons learned. The well planning included the following:Location selection criteria for avoiding shallow hazards while meeting geological objections,Pre-drill pore pressure and fracture gradient estimation,Hydraulics design and its relationship to drill string selection,Casing and wellhead program objectives,Landing string design,Lost circulation assessment,Mitigation of annular pressure in trapped annuli, andThe implementation of test rams to reduce BOP testing times.The execution section of the paper describes experiences encountered and the technologies utilized.IntroductionThe Deepwater Pathfinder spudded the Spa well on January 29, 2002, in 6,654' of water. Figure 1 presents the planned casing depths with planned contingency strings, and the actual casing depths for the original hole and the bypass hole. The original well plan was to drill to 31,600' MD / 31,000 TVD (all depths in this paper are MD unless otherwise stated). This well plan measured 10,121 on the Dodson Mechanical Risk Index, a Gulf of Mexico industry-benchmarking tool.The original wellbore was drilled to 27,504' when hole problems led to a decision to bypass. The bypass hole drilled a step out from 14,992' to 29,452' and achieved all of the geologic objectives of the well. The original hole required 146 days to complete and the Days versus Depth curve is presented in Figure 2. The bypass hole required 82 days to complete and the Days vs Depth curve is presented in Figure 3.The rig crews are to be commended for achieving zero Medical Treatment Cases and zero Lost Workday Cases during the 228 days and 325,000 man-hours.Well Planning — Location SelectionSeafloor location selection was based on avoiding shallow hazards and the ability to set 22" conductor casing in salt prior to installing BOP and riser. Entering salt as soon as possible reduced the need for the contingency 18" and 16" casing strings. The industry has realized thick salt sections act as a casing string. Two different seafloor locations were evaluated. Location #1 had a relatively flat seafloor with negligible shallow hazards potential but had no salt. Location #2 was in a highly faulted seafloor graben with a 700' escarpment that had a shallow, thick salt section, Figure 4. Detailed shallow hazards analyses were performed at location #2 and minimal shallow gas and water flow potential were predicted. Location #2 was chosen due to the ability to set 22" casing into salt.Pore Pressure and Fracture GradientOne of the greatest uncertainties in planning the well was predicting pore pressure and fracture gradient below the thick salt body. Pre-drill pore pressure estimates above salt were derived by analyzing seismic velocities at or near the proposed well location. Pre-drill pore pressure estimates below salt were derived by correlating seismic velocities at the proposed location to seismic velocities in the nearby abyssal basin where salt did not exist. The pressure estimates were derived using stacking velocities from the abyssal basin projected up underneath the salt body. Unfortunately this technique was highly reliant on the quality of the seismic data, and could not fully take into account disruptions in sediments caused by the emplacement of salt bodies. These types of disruptions could cause reduced pore pressure and fracture pressure below salt. Keywords: bypass hole, bicenter bit, original hole, fracture gradient, drill string, upstream oil & gas, requirement, hole section, spe iadc 79810, liner Subjects: Drilling Operations, Pressure Management, Drilling Equipment, Drilling Fluids and Materials, Well control This content is only available via PDF. 2003. 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