Boon or Bane? A Survey of the First 10 Years of Modern Multilateral Wells

Abstract

Since their introduction in 1993 the modern multilateral systems and their applications have developed rapidly. System capabilities and features have adapted to a myriad of operating conditions and demands placed upon them. But in many cases the development of equipment has outstripped the industry's ability or willingness to adapt it. There are two main reasons: Reliability: Despite high technical and economic success rates in a wide range of applications the common perception of multilateral technology is that it is "risky". However industry-wide statistics show that Multilateral Technology (MLT) is not the high-risk technology it is often perceived to be. Value: Even the Operators most experienced in multilateral technology struggle at times with identifying and quantifying the true value and return on investment of these wells. It is understandable there is some uncertainty when assessing the true economics of this type of well. One issue with this is the inability to perform effective modeling and prediction of well performance and lateral contribution. A second is the expense to provide equipment to actually monitor the production from additional laterals. Tangible (or Intangible) Rewards vs. Perceived Risks. This paper will examine these arguments using industry data and information and by examining actual multilateral case histories from the first 10 years of multilateral developments. This paper will also take a look at the future of this technology and discuss what may happen in the next 10 years. Introduction Thousands of Multilateral wells have been drilled in the last ten years; the vast majority is simple open-hole sidetracks (TAML Level 1) that require conventional directional drilling equipment to implement and produce1. In many areas of the world these types of wells are a common occurrence. This paper will focus on the more complex TAML levels 2–6 which utilize specialized equipment during the construction phase when moving through the drilling and completion operations. These wells have been installed in almost every major operating area world wide, from shallow, land based operations to the deep water environments of the North Sea. There have been hundred's of these successfully drilled and completed, in fact, there have been whole fields developed with this technology. Yet the industry's perception of MLT is much different. Why is this? Does the multilateral create such a disjoint, such a fork in the road that the majority of the industry becomes almost paralyzed at the mere mention of the term? We will examine several case histories, both good and bad, along with the results. The reader will then be left with additional information in order to judge whether MLT has been a boon or a bane for the Energy Industry? Case Histories - The Boon Canada - Weybourne Field Discovered in 1954, the Weyburn Unit covers an aerial extent of approximately 180 square kilometers. The Unit is located in southeastern Saskatchewan, Canada and has been operated by PanCanadian Petroleum Limited since 1963. The Weyburn Field was initially developed with vertical wells on 32 hectre spacing. A field-wide water-flood was initiated in 1964 using 151 inverted nine-spot patterns. Eventual production declines in the Unit led to an infill drilling phase which occurred between 1985 and 1992. A total of 157 vertical infill wells were drilled on both 24 and 16 hectre spacing during this time period. By 1992, it became clear that the drilling of additional vertical wells in the Weyburn Unit would not be economic2. This situation was largely due to the following factors:Remaining vertical infill targets had limited reserves (less than 4 meters of pay and an effective wellbore radius of less than 100 meters.Problems were encountered in effectively stimulating the pay zone without breaking down into an immediately underlying highly permeable water-saturated zone.Problems with the primary cementing of zones with different pressures and geo-mechanical properties frequently resulted in ineffective zonal isolation and high water cuts