Efficient and Consistent Sidetracking Operations Lower Production Costs While Minimizing Footprint in Shallow Re-Entry Wells

Abstract

In California, re-entry projects to sidetrack existing wells are a common method of accessing reserves while avoiding the process of obtaining permits for drilling new wells. Utilizing existing assets reduces the cost associated with surface footprints and partial well construction and lowers environmental impact. Recent improvements in consistency and efficiency during casing exit operations have enabled operators to minimize spend and well construction time, which makes these sidetracks more economical.

The majority of offshore and onshore re-entry wells in California require that casing exit operations be performed at shallow depths of less than 2,500 ft. Installations closer to the surface can be challenging with regard to weight limitations and an increased likelihood of a poor cement bond on the backside of casing in soft formations. Smaller workover rigs with limited torque output on land operations can also add a layer of complexity. Through collaboration during the planning process, modifications to off-the-shelf technology, and application-specific procedure adjustments, single-trip success rates and milling times have dramatically improved in the past few years.

An analysis of data from one hundred consecutive shallow casing exits from 2016 and 2017 in California shows that single trip performance was lower there compared to the average in other areas of the US and world. After an in-depth look at the installs, it was determined that a change in mill dressing and slight increase in torque output on some of the rigs could make operations more consistent and efficient. One hundred consecutive exits from 2018 to 2021 in the same geography and depths prove the implementations to have a notable improvement. In fact, the single-trip success rate improved from 84 percent to 100 percent and average mill times decreased by 35 percent.

This paper shows that reliable and efficient casing exit installations are ongoing in challenging shallow re-entry applications. This discovery provides the industry an opportunity to replicate these successes in similar assets where new drills are either uneconomical or undesirable.