Horizontal Infill Well With AICDs Improves Production in Mature Field
Authors: Carpenter Chris 
Published: November 2019

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 195450, “Horizontal Infill Well With AICDs Improves Production in Mature Field: A Case Study,” by Ilhami Giden, SPE, and Michael Nirtl, SPE, OMV Austria; Hans Thomas Maier, SPE, University of Leoben; and Ismarullizam Mohd Ismail, SPE, Tendeka, prepared for the 2019 SPE Europec featured at the 81st EAGE Annual Conference and Exhibition, London, 3–6 June. The paper has not been peer reviewed.

This paper compares the performance of three mature-field horizontal infill wells, one of which is completed with autonomous inflow-control devices (AICDs). Two of the horizontal infill wells are targeting attic oil in an area with low risk of gas production; one of these two wells is completed with slotted liners and the other with AICDs. The third horizontal well was placed in an area with higher gas saturation. The AICDs were found to choke back a high amount of fluid and keep the water cut at a stable plateau•level.

Field Introduction

Matzen is a supermature oil field northeast of Vienna and is one of the largest onshore oil fields in Europe. The field consists of several stacked reservoirs, of which the 16th Tortonian horizon (16.TH) is the largest. The westernmost part of the 16.TH is called the Bockfliess area. In this area, 77 wells are currently active: 62 are production wells and 15 are injection wells. During 2011 to 2015, the last major field-redevelopment project in the area, with the objective of doubling the gross production rate, was executed. One goal of the project included a conversion from low-rate sucker rod pumps (SRPs) to high-rate electrical submersible pumps (ESPs). Horizontal infill wells were also drilled to optimize the ultimate recovery in the reservoir.

The 16.TH sandstone reservoir lies between –1490 and –1455 m TVDss [total vertical depth subsea (i.e., total vertical depth minus the elevation above mean sea level of the depth reference point of the well)], with excellent permeability and an average porosity of 27%. Reservoir temperature•is 60°C and current reservoir pressure is 120 bar. Oil gravity is 25•°API, while oil viscosity is 5•cp. Average water cut exceeds 97%.

AICD Technology

In recent years, several different types of AICDs have been designed. The most common device types are fluidic-diode, electrical-resistivity, and rate-controlled-production (RCP). This paper covers the RCP type. The working principle of RCP AICDs differs from type to type.

The Levitating-Disc AICD. The AICD that is installed in Well BO 208 is an improved version of the RCP. The design works on the principle of a levitating disc. The AICD valve restricts the flow rate of low-viscosity fluids. When gas or water flows through the AICD valve at the same drawdown, the velocity of the water and gas will increase, reducing the dynamic pressure and levitating the disc toward the inlet to choke the flow.

The AICD valve is assembled as part of the sand-screen joint. The reservoir fluids enter the completion through the sand-screen filter and flow into the in-flow-control housing where the AICD is mounted. The fluids then flow into the production stream to the surface together with the production from the rest of the screens.