Case Study of a Large Conventional Oil Pool Discovery in a Mature Basin: The Upper Mannville of the Western Canada Sedimentary Basin

Abstract

The Western Canada Sedimentary Basin has a complex depositional and structural history and hosts many hydrocarbon deposits in numerous horizons and play types. The Basin has been explored and exploited for over a century and has over 600,000 wellbore penetrations. Some of the producing horizons have been exploited more than others, with the Albian aged Upper Mannville (UM) zone being one of the least exploited units. In the southern portion of the basin, the UM was dominantly deposited in a coastal plain environment, making it difficult to map and predict due to the inconsistent and unpredictable log based marker horizons. In addition, the reservoirs have subtle log characteristics due to the lithic nature of the sands. This talk will provide some background on how the pool of interest was discovered and the technical details of the pool itself.

The Altura Energy Inc. (ATU) discovery well was drilled in July 2016 with the drilling of the horizontal well 13-15-48-26W4 located 20 miles southwest of Edmonton, Alberta in the Leduc-Woodbend (LWB) field. This field was the site of the first large commercial oil pool discovery (Frasnian aged Leduc formation) in the Basin by Imperial Oil in 1947 and heralded the birth of the modern oil and gas industry in Western Canada. Hundreds of wells were drilled in the field in the 1940s and 1950s and by 2016 there were approximately 2400 wells in the field. The 13-15 well was drilled to a depth of 1350m TVD based on the geological mapping of many of these old wells with almost 700 of them penetrating the UM sand, all with missed pay indications. In the LWB area, the UM transitions from a channelized coastal plain environment into a marginal marine environment to the north. This provides the perfect setup to trap hydrocarbons updip against the sand pinchout edge. In this area, the sand body maps as a large wave dominated delta system roughly 130 square miles in size. This oil pool has remained undetected for so long because of a combination of subtle log characteristics, poor correlation relationships for mapping purposes and a relatively inactive area for competitors. The key to successfully exploiting this zone is the implementation of horizontal drilling and multistage fracing.

Key reservoir details will be presented and discussed but most notable is that the pool is approximately 500mm barrels OOIP, making it one of the largest conventional oil pool discoveries in the Western Canadian Sedimentary Basin in the last 20 years. ATU has tied up just over sixty sections of land in the pool through Crown land sales and freehold leasing. Development has occurred methodically, with four horizontal wells drilled to date. Drilling has been successfully accomplished with the use of existing well control to pick both bottom hole locations and landing depths. Seismic usage has been ineffective as the sand is too thin to resolve. Horizontal wellbore lengths vary from 1 to 1.5 miles and the wells are fraced with 20 tonnes of sand per stage and 30-45 stages per well. Individual well performance with be shown and initial indications show optimal pool development of 4 to 8 wells per section which will provide many future locations for the company.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018