Comparison of Matrix Stimulation of Thick Carbonate Formation: High Rate Acid and CT Acid Treatments - A Case History

Rachmawati, Fitria Dewi (PT Medco E&P Indonesia) | Andika, Rizky (MEDCO E&P Indonesia) | Simanjuntak, Timur (MEDCO E&P Indonesia) | Aimar, Amritzar (PT Medco E&P Indonesia) | Wijaya, Rio (PT Halliburton Indonesia) | Abubakar, Prihatiningdiah (Halliburton Energy Services Group)

OnePetro 

Abstract Most of oil and gas wells in Indonesia are developed in Sumatra and Java. Central Sulawesi is one area in Indonesia that previously didn't really have high activity in oil and gas because of its location that drives the logistics to become an issue. Central Sulawesi now is showing more activities on oil and gas exploration and production with the presence of Tiaka field that produced about 2,981 BOPD (Dec-07). This paper covers several stimulation works performed in Tiaka field, Central Sulawesi. The produced oil is being temporaryly stored in an FSO facility and then transported to refinery in Indonesia or exported. Tiaka wells are drilled at some angles into Tomori formation, a thick carbonate formation which ranges from 70' - 131' in thickness containing 28 API oil. Porosity varies from 10% - 15%. Four wells (Tiaka #5, 6, 7, 8) were completed with cemented casing and perforated across the target zone. Two wells (Tiaka #9, 10) were completed with uncemented preperforated liner across the target zone. Length of perforation for stimulation work ranges from 170' - 840'. Combinations of hydrochloric acid and acetic acid were used and the composition was held constant for all acid stimulated Tiaka wells. However several acid volume loadings (in gal per ft of interval treated) were tried to optimize the treatment. Several acid placement methods were tried: high rate acid treatment with gelled acid and acid through CT. All stimulated wells showed significant production increase compared to their production rates prior to stimulation. Discussion is made on which methods gives the best production result for the existing wells and the preferred method of stimulation for the future Tiaka development wells. This paper details the application of acid stimulation works in 5 Tiaka wells, post treatment well performance, best practices, and lessons learned. Introduction Tiaka field is located in the offshore Toili Area of Senoro - Toili Block, Central Sulawesi, a part of operation area of JOB Pertamina - Medco E&P Tomori Sulawesi (JOB-PMTS). The wells in this field are drilled from a man-made island called Tiaka Island. This field was discovered in 1985 by drilling Tiaka #1 well. It was produced after JOB PMTS drilled the first development well i.e. Tiaka # 5 in 2004, and followed by Tiaka #6, 7, 8, 9, and 10 subsequently from 2005 to 2007. The field is an oil producer and currently producing only from five wells, since Tiaka #7 only penetrated Minahaki Formation which is a gas reservoir. All wells were drilled directionally with inclination angles from 30 to 70 degree. The crude oil is processed in the surface facility built on the island and stored in an FSO facility before being transported to a refinery in Indonesia or exported. The reservoir is Tomori Limestone Formation, a thick carbonate formation with low porosity overlying sucrosic dolomites with good porosity. It mainly consists of shallow-water bioclastic platform limestones, occasionally dolomitic, with minor claystones and coal. Based on well to well stratigraphic correlations, the reservoir is devided into three zones, with shale layers within it. Since the reservoir quality is generally poor, it is susceptible to formation damage caused by drilling and completion fluid. Matrix acidizing is considered as one of the options to by pass the near wellbore damage and also create wormholes in the reservoir to increase the productivity. This stimulation technique has proven to be successfull and has been applied to all the development wells (exclude Tiaka #7). However, because the limestone is very thick, it is quite a challenge to apply matrix acidizing in Tiaka Field. Its remote location also drives the logistics to become an important issue.

Duplicate Docs Excel Report

Title
None found

Similar Docs  Excel Report  more

TitleSimilaritySource
None found