Four-Injector Polymer Pilot Expands to 80 New Injectors Using Modular Concept
Authors: Carpenter Chris 
Published: June 2020

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 20285, “A Successful 18% STOOIP Four-Injector Polymer Pilot Expands to 80 New Injectors in 6 Years by Adopting a Modular Concept in Grimbeek Fluvial Reservoirs,” by Juan E. Juri, Ana Ruiz, and Viviana Serrano, YPF, prepared for the 2020 International Petroleum Technology Conference, Dharan, Saudi Arabia, 13-15 January. The paper has not been peer reviewed. Copyright 2020 International Petroleum Technology Conference. Reproduced by permission.

The complete paper presents steps to accelerate enhanced oil recovery (EOR) in a Grimbeek field from a four-injector pilot to 80 new injectors in a rapid deployment. The authors focus on a simple modular strategy rather than iterating multiple possible engineering solutions to distribute polymer across the field.

Methods

The goals of the Grimbeek field-development plan include development of the field with a capital expenditure of $4-5/bbl or less and an operating expense (OPEX) of $7-8/bbl or less. The development risk is minimized through the use of a mobile deployment based on the plug-in concept that uses existing waterflooding installations and a sweet-spot-based agile strategy. The authors plan for a surfactant pilot for a second rotating cycle across the field.

The polymer used in the pilot was Flopaam 3630S. The incremental reserves were predicted from simulations that represent an incremental recovery factor per stratigraphic sequence. Rather than using early integration of studies and anticipation of facilities definitions, the authors fast-tracked the integration of laboratory and reservoir/architecture data. Tasks performed during the evaluation study are discussed in detail in the complete paper.

Reservoir Model Construction. The Grimbeek field is in depths of 1000 to 1300 m in the El Trebol formation corresponding to a fluvial environment. Total oil reserves are estimated to have an approximately 40% recovery factor (base case) or 50% (upside case). These reservoirs are a complex of fluvial unconsolidated sands.

Reservoir quality is excellent, with multidarcy permeability and porosity up to 28%. The oil is viscous (120 cp at 60°C reservoir temperature). Between five and seven stratigraphic sequences are grouped into two to four zones in each well. The reservoir has favorable conditions (low salinity of 11,000 ppm, low hardness of approximately 200 ppm, and a low temperature).

The geological model was initially a merging of the three models, which allowed tracking of the fluvial channels across the three reservoirs. These reservoir models have many grid cells (more than 1.5 million active cells). Running the models separately saves time. The individual models were run to investigate the effect of many geological uncertainties.

The Grimbeek block has three reservoirs, each a standalone simulation model (Grimbeek II, Grimbeek Norte, and Grimbeek Norte II). These reservoirs are independent from a dynamic point of view. The history match of the waterflood suggests a relatively high value of vertical communication, a crucial element to benefit from crossflow during polymer flooding.