TSO Frac-Packing: Pilot Evaluation to Full-Scale Operations in A Shallow Unconsolidated Heavy Oil Reservoir
Authors: Putra P.H. , Nasution R.Dj. , Thurston F.K. , Moran J.H. , Malone B.P. 
Published: December 2007

This paper discusses a Pilot evaluation of Tip Screen-out (TSO) Frac-Packing completion performed in a shallow and unconsolidated heavy oil reservoir in the Duri Steamflood Area, DSF. This project would be used as a base line for the full scope development of the Rindu formation, a shallow, heavy oil, unconsolidated sandstone. Mini Frac analyses, consisting of calibration and step rate tests, showed varying reservoir responses between adjacent wells, such as: closure pressure, fluid efficiency, parting pressure and rate.

Post-fracture production tests in the pilot wells demonstrated fluid productivity increases of 28% to 162%.

The results realized from the pilot project led to the use of this fracturing technique as the completion of choice for the vertical expansion of the DSF project to include the shallower Rindu Formation.

Introduction

Screenless Frac-Pack completions are a new alternative technology to complete the Rindu formation in DSF. These completions consist of a tip screenout (TSO) fracture, using Curable Resin Coated (CRC) sand. These treatments are performed without a gravel packed screen in the well. The Rindu formation consists of four sands divided by shale layers. These Rindu sands are the main target of the DSF vertical expansion project. This formation had not been previously developed as a steamflood zone because it was a secondary target after the completion of the Pertama and Kedua (PK) Sands.

The depth of the Rindu Sands varies between 300–500'. Porosity's and permeability's vary from 30 to 35% and 1300 to 3000 md, respectively. The Rindu sand contains heavy, viscous oil (22 API gravity and 160 cps), at initial conditions. Pore pressures range from 85 to 136 psig. Treatment pressure matching indicates the Young's Modulus to be less than 100,000 psi.

A twenty well Rindu Pilot was established to test the feasibility of steamflooding these sands. This project was initiated in 1994 with seven cased-hole gravel packed producers (CHGP), six open-hole gravel packed producers (OHGP), three steam injectors and four observation wells. The gravel pack completions used 20-40 Mesh silica gravel and 0.012" wire-wrapped screen liners. Open-hole gravel packed and CHGP completions were utilized to obtain a direct comparison of the production performance. Open-hole gravel packed completion is the most common type of completion in the PK sands of DSF. Previous production history in Duri showed that CHGP wells produce fluid at 40% less rate than OHGP wells. It was assumed most Rindu producers would be cased hole re-completions to co-mingle with PK production. Low cased-hole productivity provided the incentive to investigate new completion technology. Pilot tests on fracturing technology were successfully performed on four cased hole wells in the Rindu Pilot area during December 1995 and January 1996. Post-fracture production tests in the pilot wells demonstrated fluid productivity increases of 28% to 162%. Incremental production was gained due to the successful bypassing of near-welIbore damage and elimination of the gravel pack completion. A secondary benefit of the high conductivity fracture, using CRC sand, is that it performs as a sand control technique.

Rindu Completion Strategy

The primary goal of the Rindu TSO Pilot was to demonstrate productivity increase; sand control was a secondary goal. Various completion techniques were investigated in an attempt to achieve both goals.

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