Preparation of Implementation of MEOR by Nutrient Injection in Bentayan Field, South Sumater

Abstrak

Biostimulation is a technique of Microbial Enhanced Oil Recovery (MEOR) to increase oil production by injecting nutrient to stimulate indigenous microbes within the reservoir. This technique is more preferable than any other method because of its low cost, less environmental impact, and applicable in reservoir with high temperature. Molasses and fertilizers such as diammonium phosphate and NPK fertilizer are the nutrient that can be used for biostimulation which available commercially. The characteristic of Bentayan Field in South Sumatera has been observed and met the screening criteria for being a candidate for the implementation of nutrient injection with particular characteristics specifically high reservoir temperature (200° F) and heavy-oil properties. BN-81 well were selected for implementation of huff and puff nutrient injection that has high water cut value (99%). Laboratory study and statistical approach has been conducted to obtain optimum nutrient composition and resulted the ratio of 7.2% molasses, 0.31% diammonium phosphate, 0.28% NPK fertilizer composition and the addition of 0.1% NaNO3. Nutrient injection in BN-81 well were implemented in several stages starts from injection program preparation, nutrient supply, surface facility preparation, and workflow procedure. Quantity of nutrient for injection in BN-81 well consists of 16,500 kg molasses, 500 kg DAP, 500 kg of NPK fertilizer, and 200 kg of NaNO3, alongside with adequate amount of brine water for mixing process. Brine water that used for mixing and injection process has to be without chemical treatment in order to prevent hydrocarbonoclastic bacterial growth suppression. Equipment that used for nutrient injection are 1 unit of GJE rig, 2 unit of rig tank (200 bbls), 1 unit of injection pump, 1 unit of batch-mixer (100 bbls), and 1 unit of storage tank (200 bbls). Nutrient injected into reservoir in 1253-1255 m interval by 1000 bbls of nutrient with intermittent technique with 1-2 BPM injection rate. Soaking for 14 days after nutrient injection, post-flush by 2000 bbls of brine water and soaking for 7 days sequence were implemented before monitoring period.