Understanding Diversion with a Novel Fiber-Laden Acid System for Matrix Acidizing of Carbonate Formations

Day 2 Mon, December 07, 2015

Burgos

Delgado

et al. 2015

An innovative methodology using a new bottomhole flow measurement tool and distributed temperature surveying was used to treat two openhole carbonate water injectors using coiled tubing (CT) equipped with fiber optics. The system capabilities were leveraged to control, in real time, the dual injection process and ensure that the treatment covered the entire horizontal section. The new level of efficiency of this approach was proven in the outstanding results of this stimulation campaign.The method takes advantage of the fiber optics present in a CT string to acquire, in real time, both downhole flow measurements and distributed temperature surveys to identify areas of higher and lower injectivity along the wellbore. It also enables clear and rapid evaluation of the depth to the level that bullheaded fluid would normally reach downhole. The real-time flow measurement is further used to optimize the stages of the treatment that aim at placing fluid across the interval initially poorly covered, as it gives direct feedback of the efficiency of the pumping through the annulus and CT.Matrix stimulation in water injector wells is often handled in a straightforward way by simply bullheading the treatment from surface. Used within the context of horizontal or highly deviated openhole wells, this frequently leads to an overstimulation at the casing shoe or along the first part of the zone of interest, and a significant section of wellbore is poorly covered or even remains untreated. The new approach not only enables visualizing where the treatment fluid goes, it also gives a new level of control of downhole injection, in real time. This new capability was taken advantage of within the context of long horizontal openhole water injectors, whose previous stimulation treatments left untouched a significant portion of the reservoir, even when complementing bullheading by the placement of treatment fluid with CT. The methodology enabled clear identification of which pumping method was beneficial to which interval. It also proved very efficient, leading to an increase in the injectivity index of the wells of nearly threefold, beyond the expectations based on previous stimulation interventions.The new downhole flow measurement tool and its use within this innovative workflow address many limitations usually encountered during the stimulation of horizontal or highly deviated openhole water injectors. In particular, the approach enables taking full advantage of the dual injection process, which often proves difficult to control and optimize in real time. The end result is an unprecedented level of efficiency of the process.

Section: Stimulation Strategymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Innovative Methodology for Real-Time Control and Optimization of Dual Injection Increases Efficiency of Carbonate Stimulation in Horizontal Openhole Water Injectors

Day 2 Mon, December 07, 2015

Burgos

Delgado

et al. 2015

“…Execution of matrix stimulation treatments can be obtained via bullheading, or using CT for fluid placement at depth, or even by dual injection using both at the same time (Cohen et al 2010;Kalfayan and Martin 2009). Both techniques can utilize mechanical (e.g., bridge plugs, packers) and chemical (e.g., particulate diverters, self-diverting acids, and foams) means for diversion of the treatment fluids.…”

Section: Introductionmentioning

confidence: 99%

Advanced Understanding of Matrix Stimulation Treatments Through In-Job and Post-Job Evaluation of Real-Time Downhole Measurements with Coiled Tubing: A Case Study

Ahmed

SPE International Symposium and Exhibition on Formation Damage Control

Baez

2014

Matrix stimulation treatments executed with coiled tubing (CT) face various challenges in terms of design, execution, and evaluation. The design phase typically relies on information that is frequently poorly known (e.g., extent of damage). Treatment pumping schedules and fluid concentrations are often determined based on previous experience and accepted local practices. For the execution to be completed within a safe framework, the standard is to keep pumping pressures below the fracturing pressure. In some cases, tools like high pressure differential jetting nozzles are used to provide deeper penetration and lower breakdown pressures. The depths at which those tools are operated usually depend on a prior log interpretation. Finally, treatment evaluation is typically limited to the comparison of pre and post-stimulation wellhead pressures and rates.Over the past decade, numerical modeling has allowed the industry to address some of the design and evaluation challenges. Yet, the same question often remains: has the design been effectively executed and was the intervention successful? The answer depends on the choice of success criteria such as efficiency, safety, and economics.CT enabled with fiber optic telemetry-which consists of downhole gauges providing real-time data of pressure, temperature, gamma ray, and casing collar locator-has proven a game-changing technology with respect to treatment execution, improving both intervention efficiency and safety (Jacobsen et al. 2010). The provided measurements, along with the possibility to acquire distributed temperature surveys (DTS), have also shown to be the most effective solution for treatment evaluation to date.The case study presented here not only describes how CT with downhole sensors was used to optimize the acidizing treatment of an oil well producer and ensure its effective stimulation, but it also demonstrates how the real-time and DTS data were analyzed both during the intervention and through post-job numerical modeling, in order to refine the understanding of the well and that of its formation characteristics.

“…Although this notion is debatable depending on the well and formation types, as well as on the long-term vision for the well and field, fluid placement simulators are today readily available to investigate how the formation would react to specific job schedules and operational constraints. Those models are based on various parameters, such as the types of fluid used, their rheology, the formation mineralogy, reservoir properties, and the damage characteristics (e.g., Cohen et al 2010;Glasbergen and Buijse 2006;Jones and Davies 1998;Tardy et al 2007). Unfortunately, as afore-mentioned, many of those parameters are rarely known with accuracy, thus prompting engineers to sensitizing their designs and selecting the one that is most robust to unknown and/or uncertain variables.…”

Section: Introductionmentioning

confidence: 99%

“…Placement techniques may involve the use of bullheading, or coiled tubing, or a combination of both. Kalfayan and Martin (2009) and Cohen et al (2010) give extensive reviews of placement and diversion methods for matrix acidizing treatments, with their advantages and disadvantages. In most of those techniques, it is usually implied that one already knows where fluids need to be pumped along the wellbore, before starting the job.…”

Section: Introductionmentioning

confidence: 99%

Using Fiber-Optic-Enabled Coiled Tubing to Quantify Fluid Placement and Optimize Stimulation Effectiveness During Matrix Stimulation Treatments in Carbonate Reservoirs

Baez

2013

All Days

When performing matrix stimulation treatments, coiled tubing (CT) is a preferred placement technique due to the ability to spot fluid in front of the target zone(s). This method becomes a key solution when formation heterogeneities require a very selective fluid placement strategy.In today's industry, the most common approach is to design a treatment with volumes of stimulation and diverter fluids that are determined largely based on local practices. Often, it amounts to targeting a uniform stimulation, thus requiring a predefined amount of treatment fluid per length of total pay zone. That approach, although widely used and accepted, may not necessarily yield an optimum stimulation.We present an alternative technique that relies on the accurate quantification of fluid placement along the formation in order to define the respective volumes of stimulation and diverter fluids to be pumped. This method relies on the analysis of the distributed temperature sensing (DTS) data recorded by a fiber-optic line enclosed inside the CT and data processing through a fast interpretation algorithm to yield a zonal coverage profile. During a job, DTS data corresponding to the preflush can be used to estimate the initial placement distribution across the pay zone. This allows stimulation engineers to determine the best strategy for the subsequent well stimulation treatment, including fluid volumes and placement sequence. After every major pumping stage, a new DTS analysis assesses how the formation reacted to the treatment, improving placement strategy.This method has been used in multiple matrix stimulation treatments of injector and producer wells. The described innovative approach allows engineers to make more informed decisions between stages, optimizing fluid resources, fluid placement and, ultimately, stimulation effectiveness. It also leads to noteworthy advantages when designing new acidizing treatments, as companies can build on previous experience from similar wells and fields.