A ROP-Management Process in Qatar North Field

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 105521, "Implementation of ROP-Management Process in Qatar North Field," by S.M. Remmert, SPE, and J.W. Witt, SPE, RasGas Co. Ltd., and F.E. Dupriest, SPE, ExxonMobil Development Co., prepared for the 2007 SPE/IADC Drilling Conference, Amsterdam, 20–22 February. In March 2005, the operator implemented a rate-of-penetration (ROP) -management process in Qatar's North field. The ROP-management process uses real-time, customized surveillance technology to maximize continuously both drill-bit-cutter efficiency and transmission of energy to the bit. To date, the development pro-gram has been accelerated by 1 year, and USD 54 million has been saved while drilling 470,000 ft of hole. More than 440 personnel have been trained in mechanical specific energy (MSE) analysis, and 50 new field drilling records have been set. Introduction The Qatar operator currently conducts drilling operations at eight platform locations across six very-large producing blocks. The majority of wells are drilled in batch mode by section. Over the years, the operator gained extensive field knowledge and developed many efficient operating practices. Thus, the introduction of any new ROP-management process would be examined against solid baseline operating performance. At the same time, 2005 to 2006 has been a period of transition, as the company increased rig count from three to nine. The addition of many new support personnel in a multicultural working environment presented a significant challenge in terms of maintaining or improving drilling efficiency. In the midst of these challenges, the decision was made to pilot test the ROP-management process, with its first application in such an extensive carbonate-field environment. The focus of the program was fourfold:Conduct extensive customized field training in MSE analysis,implement a standard surveillance program,introduce new practices in a phased manner concurrent with measurement of energy efficiency, andcommunicate learning systematically across all rigs using MSE curves as the basis for discussion. Field Background Aside from one vertical data well at each platform, all wells drilled are 55-to-65° S-shaped directional wells with an abbreviated drop section into the Khuff reservoir. Although plat-forms are miles apart, many wells are quite similar in terms of lithology, hole size, casing configuration, and casing-setting points. An important reference data set when discussing MSE is rock unconfined compressive strength (UCS). The MSE recorded while drilling should vary as the bit traverses rock of various strengths. However, it should vary only by the amount of change in rock strength. In field operations, a baseline MSE is established, and any increase above this that exceeds the change in rock strength is likely to be an indication of bit dysfunction. Learning Cycle To begin the learning cycle, the operator analyzed historical information with hindcast MSE curves (i.e., curves generated from offset wells using existing data). Intervals of significant energy waste (high MSE) were identified and became opportunities for improvement. MSE increases beyond baseline were discussed in relation to change in rock strength. The actual energy waste visible even on the best offset was significant.