IPM Tool for Strategic Decisions: Diverse Applications of IPM in the Supergiant Tengiz Field
Authors: Kabdenov Samat , Aitkazin Mirkhat , Macary Sameh , Aitzhanov Abzal 
Published: May 2016

Integrated Production Modeling (IPM) is probably the most popular suite of software for production optimization and planning. It affords the opportunity to model the entire production system from the reservoir through the surface gathering system to the process facilities. This paper describes applications of IPM to the various strategic decisions made in Tengizchevroil LLP (TCO).

Within TCO, a full field IPM model is used for an integrated production capacity management plan considering three time periods: short, mid and long-term. Each model has its own strategic focus and is owned by a specific team, all working together in close communication. The short-term model is used to investigate the impact of field operations and surveillance on field production capacity so that all processing facilities are kept full. The mid-term model is used for debottlenecking and gathering system optimization, understanding new drilling hook-ups, and impact of workovers on system capacity. This model uses a time window of up to five years and is also used for Business Plan support. The long-term model, which is the core of this paper, focuses on major capital projects and is typically run for decades.

The main objective of long-term IPM modeling is to run production forecasts while honoring surface constraints; keeping the existing and future processing facilities full is the desired outcome. The long-term model handles not only the oil system, but also sour gas injection and waste water disposal. It models all current gathering systems, with whatever modifications or short-term projects adopted by the mid-term model inclusive and future growth plans. Examples, lessons learned, and challenges of strategic decisions made by using IPM will be shown and discussed in this paper. This includes well count study, pipeline sizing, meter station assignment, timing of rigs and projects, and drilling schedule.

One of the main lessons learned was the importance of cooperation with the reservoir simulation team in unifying constraints, incorporating the impact of reservoir uncertainty on production profiles, and developing mitigation strategies for unfavorable outcomes. Other value is derived from coordinating base business IPM results with those of the design team that handles future growth projects.

Introduction

Tengiz Field is unique, super-giant, carbonate oilfield of Devonian to Carboniferous age located in the Pricaspian Basin of the Republic of Kazakhstan along the northeastern margin of the Caspian Sea (Figure 1). The field was discovered during the former Soviet era in 1979; was put into production in 1991; and has been operated by TCO since 1993. TCO is a joint venture company comprised of Chevron, ExxonMobil, KazMunaiGas and LukOil.

Tengiz reservoir has a very large areal extent; approximately 27,000 acres in area at its top and 100,000 acres at its base, with an oil column thickness up to a mile.

Tengiz Field is an isolated carbonate build-up, consisting of a single naturally fractured reservoir. The details of Tengiz geology is reported in the literature by Kenter et al. (2006) and Collins et al. (2006).

Tengiz crude oil is a sour (approximately 13% H2S), 47° API, undersaturated oil with a bubble-point pressure of 3,660 psia. The initial reservoir pressure was 11,950 psia. The field had been produced under primary depletion until 2007 when a miscible gas injection pilot project was initiated. Despite the miscible gas injection, primary depletion (rock/fluid expansion) is the principal drive mechanism at Tengiz. Current reservoir pressure is in the range of 7,500 psia with temperatures in the range of 220–240°F.

Current production is ~530,000 BOPD from more than 70 active producing wells. Tengiz field wells are cased and perforated for the most part, with a few openhole completions. Producing intervals are as thick as 2,620 ft, at depths varying from 12,470 ft to 18,040 ft. IPM is heavily utilized for production optimization and planning.