This paper presents a case study of a matrix acidizing treatment in a well located at the neutral zone between Kuwait and Saudi Arabia, whereby the combination of a "smart fluid" in a stimulation treatment pumped through a Coiled-Tubing (CT) with the real time distributed temperature sensing (DTS) technology helped improve the real-time decision process of fluid placement, temporary plugging placement, and treatment efficiency evaluation. As part of the analysis process and to facilitate the onsite decision-making process, a temperature inversion technique was also used to translate the actual temperature profiles into fluid invasion profiles across the horizontal open-hole section of the well. Additionally, a full scale acid placement and thermal modeling is proposed in order to perform an in-depth post-treatment evaluation. The bottom hole data evaluation further confirmed the benefits of using a smart fluid. Following the treatment, the well produced at a rate of 1500 bbl/day with 17% water cut, which is well below the field average of ~50%.

Low permeability oil and gas-bearing carbonate formations are routinely completed with open hole horizontal laterals and multistage fracturing treatments to achieve maximum reservoir contact and enhance production of the formations. This completion technique has been successfully used in previously non-economical reservoirs — in North America and around the globe — to make them commercial. Open hole multistage fracturing technologies have been deployed in tight gas carbonate reservoirs to improve well productivity while using reservoir simulations to optimize the fracture design. When applying multi-stage fracturing one of the key aspects is to assure the isolation between the stages to induce independent fractures. This goal becomes even more challenging to achieve when the process is an acid fracturing treatment. Hydraulic communication between the fracture stages has been previously observed, which has prevented the creation of separate fractures transverse to the wellbore, thereby resulting in fewer and shorter fractures, mostly created along the wellbore plane. In many cases, new fractures could not even initiate and only matrix acid treatments could be conducted. To overcome the isolation challenge during an acid treatment, a multistage completion assembly based on sliding sleeves and swellable packers has been devised and implemented to conduct selective acid fracturing in low permeability carbonate reservoirs. This combined system has mechanically simplified the multistage fracturing job, reducing costs and complexity compared with traditional cement and perforating methods. The system provides excellent isolation between consecutive treatments by providing positive annular barriers. The technology ensures that the entire lateral is treated uniformly and according to the design, enhances proper fracture placement, increases reservoir contact area, and improves well productivity. This paper describes and addresses the successful deployment of this completion and fracturing technology. The success resulted from careful planning, fluid testing, and a comprehensive completion design that was fit-for-purpose to provide optimal stimulation treatment and productivity enhancement.

In recent years, multistage fracturing completion has been adopted by many operators across the globe as a primary means to maximize reservoir contact. To succeed, this completion strategy must be complemented with good understanding on petrophysical and geomechanical properties of the reservoir; which resulted in a better understanding of fracture orientation and decisions on open hole length, number of fracturing stages, packers and frac ports placement.When dealing with a low permeability environment, for a specific open hole length, it is almost certain that increasing the number of fracturing stages will potentially give the highest productivity. Subsequently, this will also potentially increase the chance of having packer integrity issues due to the shorter distance between the frac port and packers.Currently, the most common practice to evaluate packer integrity is done on-site, by comparing pressure response at a constant injection rate before and after opening a frac port, in addition to observing breakdown and closure pressure for each compartment. In the event of similar pressure response on both sides, it may be an indication of communication. Consequently, relying only on this injection exclusively is not sufficient because the leak-off profiles may suggest otherwise and could lead to drawing the wrong conclusions. This paper describes a new enhancement of the mini fall off (MFO) injections procedure, which can be used to confirm multistage fracturing packer's integrity on-site. The procedure consists of performing injection with similar small volume and rate before and after opening the frac port, overlaying pressure responses, pressure decline analysis, as well as comparing pressure derivative for both injections. This technique has been successfully tested on-site where one out of seven stages planned were identified to have communication and has helped in the decision making process to skip the stage and avoid stimulating the same compartment again.

In Saudi Arabia, conventional oil reservoirs have been treated using conventional stimulation methods. The challenge is that many of the formations now are tighter and require improved stimulation methods. Fracturing is a major topic discussed in the industry as of late and as such using it in this formation will serve as a trial to shift from conventional stimulation methods to fracturing when facing tighter formations. This particular acid frac was performed in a tight carbonate formation ranging in permeability from 1 - 2 md. The chosen well is a newly drilled tri-lateral producer completed with a multi-stage frac completion in the mother bore and will serve as a pilot well for this reservoir in the area. The acid frac was a seven stage completion utilizing hydraulic fracturing. Several methods using pressure and injection were used to determine reservoir fracturing response and petrophysical properties. This paper will discuss the first multi-stage acid frac performed in an oil producer in Saudi Arabia. It will examine the entire process of candidate assessment, job preparations, and execution. In addition, the paper will discuss challenges faced, solutions taken, and the post-decision results. The paper will show how an injectivity test performed pre- and post-frac was used as a benchmarking tool to analyze the effectiveness of the frac. Finally, we will discuss the flowback of the well, initial results, lessons learned, and optimization of future jobs.

Several unknowns still remain in carbonate matrix acidizing. Poor correlation between porosity and permeability in carbonate formations, the possibility of natural fractures and limitations in the economically practical number of core samples often result in a largely unknown permeability variation across the pay. Intelligent fluid systems have been developed to address such uncertainty, but the lack of real time downhole data during the treatment typically prevent confirmation of the fluid system efficiency.