The positive pressure increase effect from a displacement plug hitting the landing collar is often a signal for the end of cement displacement. Occasionally the plug is damaged by frictional wear, chemicals, and temperature, however displacement can also be affected by the mud compressibility, a complex value dependent on the downhole conditions (rheology, density, temperature, etc.) and pump efficiency, which are never truly 100 percent efficient. Using a high frequency pressure monitoring system, it is possible to detect the location of the wiper plug when passing through each casing joint as it produces a pulse that can be detected in real time, even as the displacement plug fins are worn away with friction. Controlling displacement volume is crucial for the cementing job as overdisplacement of cement can complicate the isolation of the string cemented due to contaminated cement pushed up into the annulus and under-displacement may result in extra drill out time and therefore nonproductive time in both scenarios. Testing of a novel cement displacement method by measuring pressure at high frequencies to see the pulses generated by the displacement plug passing through the casing joints consisted of validating the technology to an accuracy of one casing joint or around 12 meters. The Mexico Land analysis has shown that on average, 45 m of cement is left above the retention collar, or 45 meters of cement that was never planned to be left inside the casing. The technology demonstrated great success where casing joints have a positive internal diameter change. By combining the measurements of displacement volume and pressure pulses produced as the plug passes through a casing joint, a more accurate measurement of the wiper plug location is achieved versus conventional displacement methods.
Acid fracturing is a widely accepted method for stimulation of carbonate reservoirs. A new high-resolution fracture hydrodynamics and in-situ kinetics model integrated on a reservoir-centric exploration and production platform improves acid fracturing simulation accuracy and performance for completion, stimulation, and reservoir engineering groups. This paper describes key features of the new acid fracturing model and the workflows that have been enabled on the E&P platform. We demonstrate that the new acid fracturing model can simulate the key effects of acid fracturing at a new level of fidelity and quality. For example, it reproduces viscous fingering effects that occur naturally when alternating fluid systems of different viscosities are pumped into the fracture. The model simulates diverting agents that reduce leakoff in the fracture area and their effects on fracture geometry. Combining the 3D earth model in the E&P platform and high-resolution simulator allows the modeling of small-scale heterogeneities that affect fracture conductivity with a high level of accuracy. The model is also capable of simulating hybrid acid-proppant treatments. Finally, a fluid and materials database is incorporated to capture the impact of modern acid systems and diversion agents. The new model was validated against the results of laboratory experiments and published data. The first results of the platform stimulation-to-production workflow implementation are presented for a formation with high calcite content. The new approach enables engineers to evaluate completion and stimulation designs directly by quantifying the impact on hydrocarbon production and seamlessly integrates carbonates completion design and reservoir engineering disciplines. The novel high-fidelity approach to acid leakoff, diversion systems, and rheology of different fluid mixtures significantly extends the design and evaluation tools for acid fracturing treatments in carbonate formations. Integrating the acid fracture model and E&P platform enables simulation of multiple acid treatments all the way to production evaluation and opens the path towards optimal design of single- and multiple-well treatments.
Tight carbonate development is moving towards longer laterals requiring a higher number of fracturing stages to complete a given well. A higher stage count implies longer completion time and higher costs. Therefore, an engineered strategy using technology enablers is indispensable to reducing the number of stages while retaining the well performance objective. A 6,250-ft cemented lateral initially planned with 13 fracturing stages was analyzed for lithology and reservoir development to revise the perforation strategy to complete with more clusters per stage and reduced the number of stages to 5 stages. Clusters were designed to be very narrow to effectively divert the fracture fluids using chemical diversion. For a successful stimulation evaluation, a novel pressure monitoring technique was used to analyze the fluid entry points from the water hammers. Pills of multimodal particulate near-wellbore diverters were used across the lateral to stimulate the perforated clusters in only five fracture stages effectively. The multimodal particle distribution model allows for bridging and then creating an impermeable flow barrier to ensure diversion. Effective diversion was seen through a pressure increase when diverter entered the formation. Correlations were analyzed for diversion pressure dependence on pill volume and injection rate to improve diversion. A new algorithm for nonintrusive diagnostics was also deployed. The algorithm combines advanced signal processing with a tube wave velocity model based on Bayesian statistics and has no additional operational footprint. The program allowed a timely interpretation to evaluate the fluid entry points based on the water hammer events. This evaluation was compared to the intuitive stimulation sequence based on the lithology to explain the results. The comprehensive analysis demonstrated the lateral was stimulated effectively. Finally, the production performance was compared with two offset horizontal wells intersecting the same carbonate sublayer. Offset 1 was a cemented lateral completed with 12 stages, and offset 2 was an openhole packer and sleeve lateral completed with 7 stages. Analysis of the post-fracturing absolute production enhancement showed 11 to 15% improvement and production index (PI) improvement was 40 to 63% when normalized by stage count. The paper presents a rare and unique strategic integration of multiple technologies. This success paves the way for similar future developments to enhance operational efficiency and allow significant cost savings.
During the primary well cementing operation, when the cement slurry is pumped into the annulus around the outside of the casing string, it is very critical not to over displace and let the displacement fluid enter the annulus. Traditionally, to determine when to stop the cement displacement operation, the top cement plug position is tracked volumetrically by dividing the displaced volume by the casing internal cross-sectional area. However, the volumetric method is prone to uncertainties related to displacement fluid compressibility, high-pressure pump inefficiency, flowmeter inaccuracy, and variance in casing joint diameters. The new cost-effective cement displacement monitoring method is based on the analysis of the pressure pulses generated by the top cement plug passing the casing. These pressure pulses are detected by the standard pressure transducer installed at the cementing head. When correlated with the casing tally, these pulses identify the plug position related to the completion elements that provide better accuracy than the volumetric method used conventionally. The case studies include the successful cement displacement monitoring example and the case where the plug was prematurely stopped 90 meters above the landing collar, which was revealed by the subsequent drilling and confirmed independently by the new plug tracking method.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.