Throughout the last few years, oil company strategies have moved toward recovery of the maximum oil in place from mature fields and reservoirs that were previously considered technically challenging. The Mauddud formation in the Bahrah field is a low permeability carbonate formation with moderate to high oil viscosity. Viscosity is between 2 and 7 cp at 170°F, but a 90-cp viscosity at surface conditions is commonly observed once a well is placed on production, creating challenges for a vertically drilled well that could not provide necessary levels of sustainable production. In an attempt to achieve economic continuous production, a 3,000-ft lateral horizontal well was drilled. The lateral length was designed as an optimal solution for such a challenging reservoir to help sustain the production flow. Additionally, a multistage acid fracturing (MSAF) treatment was performed. This paper discusses the design, execution, and production of the first MSAF treatment performed in the Mauddud reservoir using a cased openhole completion with swell packers and sliding sleeves that were placed in seven stages across the 3,000-ft lateral interval. Post-operation analysis exhibited highly sustained production, creating a shift in oil company plans toward drilling new horizontal wells and applying MSAF treatments to move the Bahrah field into the development phase. Results obtained from this operation were effectively used to help improve production in similar mature formations. Based on this pilot treatment, a wide-scale field development strategy was planned, and many wells were drilled, completed, and fractured similarly in Bahrah field.

A significant challenge in the mature South Kuwait Burgan field is assuring maximum hydrocarbon flow through high water-prone sandstone intervals. Recently, water control or conformance treatments have been considered to make oil production from these reservoirs more economically feasible. This paper discusses the application of a novel downhole chemical methodology that has created a positive impact in overall productivity from this field. The production profile in this field has been challenging in terms of increasing water volume, which poses a great threat to continued economic viability and may lead to lower production rates, a reduction in recoverable reserves, and premature abandonment. Some of the production-gathering centers cannot handle the ever-increasing volumes of produced water and are operating beyond design capacity. In order to solve this challenge, a downhole chemical treatment was modified as a fit-for-purpose treatment to address the unique challenges of electric submersible pump (ESP)-driven well operations, formation technical difficulties, high-stake economics, and high water potential from these formations. A unique hydrophobically modified water-soluble polymer (HRPM) was implemented in a high water-cut well to selectively reduce water production. Because this well was producing with an ESP, the treatment was pumped down the annular space. A preflush was pumped ahead of the HRPM treatment to remove deposits that could prevent the polymer from effectively adsorbing to the rock surface. The treatment was then overdisplaced with brine. This technology incorporates an HRPM that is adsorbed on the rock surface, resulting in the alteration of rock surface characteristics. The hydrophobic modification to the base polymer chain adds unique associative properties to the system, which selectively reduce the water's effective permeability in the reservoir, impeding water flow and facilitating increased hydrocarbon flow. A direct result of the implemented treatment is that the post-operation well test and production data show a high sustained hydrocarbon production at a smaller choke size with significantly reduced water cut. This successful treatment confirmed the optimized conformance technology as a solution for the first well in this field. In order to achieve maximum reduction in water production, this technology is customized based on the temperature and permeability of the treatment zones, thus ensuring it is fit-for-purpose. Furthermore, this paper summarizes the candidate selection, design processes, challenges encountered, production response, and lessons learned from this treatment and can be considered a best practice for addressing high water production challenges in similar conditions in other fields.

The proper fracture stimulation of high-pressure/high-temperature (HP/HT) carbonate formations completed with horizontal wellbores is a challenging task for any operator or service company, particularly because of concerns associated with HP/HT, acid reactivity, completion and production equipment corrosion, and acid distribution. The case history presented in this paper describes the performance of an acid fracture intervention in a HP/HT well where, because of a number of problems encountered during the well construction stage, this intervention was the last procedure considered to evaluate the productivity of a Marrat formation well. In view of the stimulation challenges encountered, the architecture of the wellbore, and the intervention stimulation requirement to evaluate the productivity of the horizontal well completed in the Marrat formation, it was necessary to change the proppant fracture stimulation technique originally planned. Instead, it was decided that a selective acid fracture stimulation would be performed in the prospective part of the horizontal section where three long perforation clusters had been placed. Acidizing fracture stimulation was performed in one intervention using a next-generation liquid and soluble solid diversion system that enabled the generation of one selective fracture per perforation cluster. The planned acidizing fracture stimulation process was implemented properly in the field in accordance with the design constraints. The reactive fluid system diversion and the generation of a new fracture when the diversion system reached the perforation were clearly observed. The post-acid fractured well productivity index (PI) showed the high quality of the stimulation performed in a challenging environment, demonstrating the effectiveness of the new diversion system for creating selective fractures in a horizontal wellbore with multiple perforation clusters. Considering the well's architecture, HP/HT nature, and single intervention requirement, the case study documented in the paper can be helpful in the decision-making process when selecting a proper stimulation technique for challenging conditions. The effectiveness of the new diversion systems is also discussed.

The unconventional Bahrah field is a high potential field which poses several challenges in terms of hydrocarbon flow assurance through highly heterogeneous tight carbonate intervals with poor reservoir quality and curtailed mobility. Due to this, the field development strategies have prioritized well completion using horizontal acid fracturing technology over vertical wells. During fracturing, the acid system tends to form highly conductive channels in the formation. Most of the fluid will flow into the path of least resistance leaving large portions of the formation untreated. As a result, the fracturing treatment options dwindle significantly, thus reservoir stimulation results are not optimum in each stage. Achieving complete wellbore coverage is a challenge for any acid frac treatment performed in long lateral with variations in reservoir characteristics. The multistage acid fracturing using Integrated Far-field Diversion (IFD) is performed using selective openhole completion, enabling mechanical annular segmentation of the wellbore using swellable packers and sliding sleeves. The mechanical as well as chemical diversion in IFD methodology is highly important to the overall stimulation success. The technique includes pumping multiple self-degrading particle sizes, considering the openhole annular space and wide presence of natural fractures, followed by in-situ HCL based crosslinked system employed for improving individual stage targets. A biomodal strategy is employed wherein larger particles are supplemented with smaller that can bridge pore throats of the larger particles and have the desired property of rigidity and develop a level of suppleness once exposed to reservoir conditions. The IFD diversion shifts the fracture to unstimulated areas to create complex fractures that increase reservoir contact volume and improving overall conductivity. This paper examines IFD in acid fracturing and describes the crucial diversion strategy. Unlike available diverters used in other fields, the particulates are unaffected at low pH values and in live acids. Proper agent selection and combination with in-situ crosslink acid effectively plug the fracture generated previously and generate pressure high enough to initiate another fracture for further ramification. The optimization and designing of the IFD diversion in each stage plays a key role and has helped to effectively plug fractures and realize segmentation. Concentration of diversion agents, volume of fluid system and open-hole stage length sensitivity plays vital role for the success of this treatment. The application of IFD methodology is tuned as fit-for-purpose to address the unique challenges of well operations, formation technical difficulties, high-stakes economics, and untapped high potential from this unconventional reservoir. A direct result of this acid fracturing treatment is that the post-operation data showed high contribution of all fractured zones along the section in sustained manner. Furthermore, this methodology can be considered as best practice for application in unconventional challenges in other fields.

The execution of pinpointed multi-stage acid fracturing inside 4-1/8-in. slim horizontal open hole sections is discussed. For the first time in Kuwait, pinpoint stimulation of 16 frac stages across a total 4,666 ft open hole while commingling three reservoir sections in very low reservoir quality carbonate rock was performed. Pumping rates were optimized while managing differential sticking hazards in the implementation of this frac procedure. Electric submersible pump completion deployment and well testing enhanced production by more than 100% over the anticipated rate. Stimulation parameters were optimized with 2-7/8-in. tubing as the frac string for greater reservoir penetration and productivity enhancement. Differential sticking was addressed by removing drilling filter cake prior to the frac job. Possible risks were evaluated, and mitigation plans were implemented which resulted in the successful application of multi-stage acid fracturing across the open hole.