Delaware Basin Drilling
Authors: Elliott D.G. , Gordon J.C. , Norris M.W. , Torres L. 
Published: December 2007

Abstract
Many operators are now very active on drilling operations to reachPennsylvanian and older formations in the Delaware basin of West Texas. Deepdrilling in the basin has been sporadic since 1937 but larger rigs, improvedmud programs, better bits, stronger tubular goods, designed cementing programs, specialized tools and drilling programs to utilize these advanced materials andother techniques have permitted more economical drilling in recent years. Concentrated development drilling in certain areas has encouraged furtheradvances in technique and has decreased costs.
Further drilling-cost reductions will be helpful in encouraging explorationand development of the unexplored areas and depths of the basin.

Introduction
Discovery of commercially productive quantities of gas from deep, largereservoirs in the older formations of the Delaware basin has causedconsiderable new drilling activity in several areas of the basin. Followingyears of disappointment and lack of commercial production, the basin hasrecently proved the Wolfcamp, Pennsylvanian, Devonian and Ellenburgerformations as sources. With increasing development and growing gas marketsencouraging each other, the result has been one of the largest West Texasdrilling campaigns in terms of dollar costs. The oil industry is now encouragedenough to invest more than $50 million in wells and facilities to find anddevelop the deeper reservoirs. Considerable time and effort are now being spenton the improvement of drilling programs to provide the most economicalexpenditure of drilling dollars available. Practices and techniques areimproving as a result of these efforts, but continued work will be needed asnew areas are drilled and new problems encountered. The Delaware basin offers alarge, varied assortment of problems and the industry is acquiring theexperience to put its technical knowledge to effective solutions.

Geology
Ancient seas laid down thick beds in the Permian Basin areas. Subsequentuplift of the Central basin platform divided the Delaware basin and Midlandbasin portions of the Permian Basin and provided conditions of similarity anddissimilarity between them. The Delaware basin portion characterized itself bythe presence of the Delaware Mountain group of sands and limes. In most cases, the Delaware basin also afforded deeper and thicker amounts of equivalentformation than the Midland basin. Movements during Pennsylvanian time of thesubsurface have furnished uplifting for extensive structuring and faultingwhich formed many traps for possible hydrocarbon accumulation.
The basin is contained within the general area shown in Fig. 1. Bounded onthe east by the Central basin platform, on the west by Diablo platform, on thenorth in New Mexico by the Capitan Reef and on the south by the Marathon Thrustbelt, the Delaware basin is a general area with well-defined boundaries. Thebasin deepens from all sides toward the east center with the sharpest changefrom the east side.

Development of the Basin
Drilling wells to the Pennsylvanian formation or 10,000 ft and deeperstarted in the late 1930's. With very little encouragement in the way ofproduction, 51 such wells were drilled before 1960. These wells included thedeepest and the fastest ever drilled, but failed to find commercial quantitiesof oil or gas.
All of the areas in the basin were touched by this drilling whichcontributed mostly information. This information affected later drillingprograms and drilling equipment could be used to advantage.