Stimulating offshore sandstone formations with depleted reservoir pressure is a challenge. The conventional practices for sandstone acidizing are to pump pre- and post-flush hydrochloric acid to minimize precipitates from the main hydrofluoric acid reacting with the carbonates, and to flow back the well immediately after the acid is pumped. However, in offshore wells, limited deck space for chemical mixing equipment and depleted reservoir conditions necessitated a retarded single-stage HCl/HF acidizing approach with nitrogen. Because cores were not available, solubility testing was performed using cutting samples with normal HCl/HF acid and retarded single-stage HCl/HF acid. The retarded single-stage HCl/HF acid outperformed the conventional HCl/HF acid in these tests. Because of the challenge in treating long perforated intervals with various permeability zones and depleted reservoir conditions, the operator chose to pump retarded single-stage HCl/HF acid with nitrogen as a diverting and lifting agent. The retarded single-stage HCl/HF acid system eliminated the requirement of pre- and post-flush HCl acid stages, reducing the treatment complexity and overall treatment time. The successful single-stage HCl/HF acid treatment resulted in a 225% increase in oil production and a 416% decrease in water cut. The decreased drawdown around the wellbore helped improve the oil-water ratio and deliver a lower water cut. This paper summarizes the challenges of testing, designing and pumping the single-stage sandstone acid system in one well offshore Vietnam.
The proposal of this paper is to share the case history and knowledge learned in this first application of the multistage zipper frac procedure and techniques in Biogenic wells. This breakthrough achievement was planned and executed by ADNOC Onshore Biogenic Drilling Department in Abu Dhabi which involves seven different services, each has a high importance and close collaboration was a key contributor to the feasibility of the project and the collective success obtained. The Zipper frac method selected and tailored by the Biogenic Team for the specific application enables to significantly increase the number of fracs per day performed over 2 wells. This technique stages multi-well completions, where wells are completed in a back-and-forth manner. One well is being pumped /fractured while the other well is being plugged and perforated for next stage. One of the key achievements in the Biogenic Zipper frac operation lies in the easy switch from line to another by using a manifold in a safe manner and without confusion. Because of the focus and high potential of Biogenic gas, Biogenic Team faced the challenge of delivering the two wells on a very tight schedule. This led the Team to review, select and implement a novel methodology that would deliver time and cost savings to the Project. New ideas were scouted and analyzed by different departments and service companies to select the most appropriate. Upon selection of the zipper frac method, meetings were done to issue and finalize a proper implementation plan for this multi-frac operation, which was a first in ADNOC Onshore. Explaining in workshops to key stakeholders and respective higher management the methodology and plan as well as the associated savings was essential to get full support and endorsement for implementing this method. There was no doubt that this method was the best way to achieve the goal with the tight given timeframe. Successful implementation resulted in of around 50 days savings compared with applying the conventional multiple frac procedure / method on a well-by-well basis. Wider application of this method represents a breakthrough in delivering future fracked wells cheaper and faster thereby bringing significant savings to future Biogenic gas development projects. Because of the importance of ongoing assessment and potential future development of Biogenic gas and unconventional resources, sharing details of ADNOC Onshore first implementation of the Zipper frac methodology is of benefit to the industry. The detailed account of its implementation (inclusive of added important technical features such as dissolvable plug and perf technology) that has delivered safely and successfully twenty-four (24) staged fracs in a short time frame represents a piece of useful knowledge.
Tight Oil Unconventional Reservoirs are challenging when it comes to development and enhancement of production. Transverse Multistage Hydraulic fracturing technique is widely used to maximize production from unconventional reservoirs, however it can be quite challenging when it comes down to execution across longer Tight Oil Horizontal laterals. The paper describes in full the various aspect of technical and operational planning in order to successfully execute highest number of Frac Stages in a well in UAE across a lateral length of 5300 ft This paper will describe an Integrated Field development Study that included building of Geomechanical Model for in-situ stress characterization and rock elastic properties for 3D Hydraulic Fracture Modelling. The fully 3D Hydraulic Fracture model assisted in geometrically spacing, finalizing and optimizing the number of Frac Stages across the horizontal Lateral. In order to optimize the design, specialized cores studies were conducted as part of the process such as Steady State measurements of permeability. In this paper the testing part will be describe in full and how the study was incorporated in the state-of-art Frac Simulator to ensure optimized frac design and realistic deliverable. The paper focusses on the operation planning, execution and efficiency. This includes frac stages execution, pump down plug and perf, number of cluster optimization & cluster spacing, milling, cleanout and flowback. Also in order to quantify the contribution from each stage, tracer services was utilized which will be detailed in the paper. Finally the paper will also cover the Well Testing strategy, which is one of the crucial aspect of the well deliverability. API Lab and Composition Analysis of Oil & Gas Samples were also conducted post fracturing as part of the study. The overall planning and execution of this well will become a guide and will be utilized for future well and frac design, which will be discussed in the paper. This integrated approach will be utilized in planning and designing future wells. The post fracturing data and production data collected from the well will help in further Frac Stage optimization which will lead to overall cost optimization
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