Production Monitoring by Intelligent Chemical Inflow Tracers in Long Horizontal Heavy Oil Wells for the Nikaitchuq Field, Northern Alaska
Authors: Kuck M.  D. , Nofziger L. , Gentil P. , Faevelen E.  S. 
Published: March 2015

Obtaining reliable production surveillance data is not always achievable with all completion types. Two heavy oil production wells in the Nikaitchuq field in Northern Alaska hosted such challenges. The wells do not flow naturally and ESP's were chosen as the artificial lift (AL) method, thus eliminating the option of applying conventional flow profiling techniques such as production logging tools (PLT). Permanent chemical intelligent tracer systems were installed to monitor inflow distribution and water breakthrough along the long horizontal production intervals.

The nature of heavy oil fields in this area require long, horizontal production wells with adjacent injectors to drive waterflood support. Lateral production conformance in this area was unknown or could not be definitively confirmed. A means to understand inflow performance along laterals in order determine appropriate lateral length and optimize waterflood design was needed. Early water breakthrough due to uneven water front and possible matrix bypass has previously been experienced in nearby, analogous fields. A means to determine the general location of water breakthrough was also desired. Oil and water intelligent tracers were chosen to provide the required information to enhance pressure management and waterflood techniques. These intelligent tracers were placed strategically along the lateral in multiple development production wells. With this knowledge in hand, other production optimization tools such as ICD's, DTS and zonal isolation packers can be assessed to help effectively manage the waterflood.

The intelligent tracer systems are designed to release unique tracer chemicals when exposed to the corresponding target fluid, i.e. oil and water contact triggers intelligent oil and water tracer release respectively. The tracer transient signatures are interpreted to assess the type, location, and quantity of fluid flow along the lateral. Re-start monitoring campaigns have been conducted for three wells during dry oil production. The data interpretation confirmed toe production in two of the wells. Quantitative estimates of inflow distribution along the producing sections were made for all wells.

Introduction

The Nikaitchuq field is located on the North Slope of Alaska, west of Prudhoe Bay (Figure 1). The field consists of an onshore site (Oliktok Point, OPP), an offshore drill site (Spy Island Drillsite, SID), a processing facility and associated infrastructure. Nikaitchuq has been producing since January 30, 2011.

The Nikaitchuq project is a 52-well development of the Schrader Bluff reservoir which contains viscous oil in unconsolidated sand. The API of the crude oil is approximately 18.7° on average. The reservoir vertical depth is approximately 3,500 to 4,000 ft TVD. The development was planned as a line drive waterflood utilizing extended reach horizontal laterals1 with measured depth ranging from 15,000 to 22,000 feet. A complex reservoir monitoring and control strategy was implemented in the field development to understand the interaction between injection and production wells along the length of the extended lateral sections. Monitoring and control for injection wells include fiber optic distributed temperature sensing with pressure and temperature gauges placed in selected locations. Passive injection control devices are also placed in the injection wells, which include a feature to control water injection at each device location2. Due to the inability of the production wells to flow naturally, electric submersible pumps (ESP) were chosen as the preferred method for artificial lift. This configuration does not allow for conventional production logging; therefore, a long term solution was required that did not require well intervention. Permanent chemical production tracers were chosen as the method for production inflow monitoring along the length of the laterals and are an integral part of the monitoring and control strategy. Three of the Spy Island Producers (SP) equipped with intelligent inflow tracers will be discussed in this paper; SP16-FN3, SP33-W3, and SP10-FN5.