American Petroleum Institute

Isolating Potential Flow Zones During Well Construction - First Edition
 N RP 65-2

Annotation

Overview

This document contains best practices for zone isolation in wells to prevent annular pressure and/or flow through or past pressure-containment barriers that are installed and verified during well construction. Barriers that seal wellbore and formation pressures or flows may include temporary pressure-containment barriers like hydrostatic head pressure during cement curing and permanent ones such as mechanical seals, shoe formations, and cement. Other well construction (well design, drilling, leak-off tests, etc.) practices that may affect barrier sealing performance are mentioned along with methods to help ensure positive effects or to minimize any negative ones. See Section 2, Definitions, for this scope's applicable parameters including types of wells, well barriers, barrier elements, etc.

Objectives

The objectives of this guideline are two-fold. The first is to help prevent and/or control flows just prior to, during, and after primary cementing operations to install or "set" casing and liner pipe strings in wells. Some of these flows have caused well control incidents that are very serious problems. They threaten the safety of personnel, the environment, and the drilling rigs themselves. The second objective is to help prevent sustained casing pressure (SCP), also a serious industry problem.

Another publication, API 90, provides guidelines on managing annular casing pressure (ACP) including SCP, thermal casing pressure, and operator-imposed pressure. These guidelines include monitoring, diagnostic testing, establishing the maximum allowable wellhead operating pressure (MAWOP), documenting annular casing pressure, and risk assessment methodologies. API 65 has been written to complement the objectives of API 90 and its recommended practices for pressure-containment barriers. Many of the definitions in Section 2 are aligned with those in API 90.