Executive Summary

Understanding the inconsistency between classic 2D fracture models and models used for falloff analysis results in the need to construct a consistent model based on falloff analysis that could match the entire injection and falloff pressure behavior. Consistent Model for Injection and Falloff Pressure Match of Diagnostic Fracture Injection Tests (DFITs) presents such a model capable of matching both the injection data and the falloff data from a DFIT. The authors apply the model on a field case to demonstrate its capability.

Predicting hydraulic-fracture-height growth is one of the critical factors in designing successful hydraulic-fracturing treatments. To illustrate the effects of modulus contrast on fracture-height containment, The Effect of Layered Modulus on Hydraulic-Fracture Modeling and Fracture-Height Containment proposes a new approach that uses the effective modulus of a layered reservoir. The study shows that the important factors that affect the effective modulus are fracture-tip locations, modulus values, and the height percentage of each rock layer.

Frac packs are the dominant completion technique applied to high-permeability reservoirs in the Gulf of Mexico (GOM). During the past few years, operators have focused on reducing skin and improving the production, leading to a more-detailed analysis of frac-pack performance. The Importance of Clean Off-Plane Perforations in all Phases of a Deepwater Well and its Productivity Impact demonstrates that in high-permeability reservoirs, production from the off-plane perforations is as important as production from the fracture. The authors examine the theoretical basis of the contribution of off-plane perforations to total flow and demonstrate the adverse effect on this contribution.

On the Sealability of Metal-to-Metal Seals With Application to Premium Casing and Tubing Connections describes the mechanisms of metal-to-metal seals using an experimental setup and a stochastic numerical sealing model. The model couples a contact-mechanics model with a flow model and takes into account the influence of all the surface-topography features by introducing the concept of seal permeability. The authors conducted experiments for a variety of thread compounds and applied pin/box surface coatings. They use the results of these experiments to validate a stochastic numerical sealing model for sealability. 

It is common practice to complete long carbonate intervals with multistage stimulation treatments, especially in horizontal wells. Zonal-isolation effectiveness is rarely evaluated because of a lack of zone-specific pressure and/or temperature data. In Review and Analysis of Zonal-Isolation Effectiveness in Carbonate Reservoirs Using Multistage Stimulation Systems, the authors review zonal-isolation results from a series of high-rate acid jobs conducted in wells equipped with zone-specific pressure and temperature gauges to investigate the effectiveness of zonal isolation during and after treatment. 

Drilling. Is it possible that the bit comes to a complete stop while the motor is forced into the backward rotation? High-Frequency At-Bit Measurements Provide New Insights Into Torsional Dynamics When Drilling With Steerable Mud Motors in Unconventional Horizontal Wells reports that the bit experienced full stick-slip behavior and drove the bottomhole assembly backward rotation by means of the action of the mud motor’s power section. This new understanding contradicts the traditional thinking of torsional oscillations in motor bottomhole assemblies.

Slimhole well design can reduce well-construction cost through a reduction in steel, fluids, and disposal costs. In the industry, there has been a misconception that slimhole size involves the tradeoff of slower rate of penetration (ROP) and less-efficient fracture treatment. Slimhole Unconventional Well-Design Optimization Enables Drilling Performance Improvement and Cost Reduction describes the implementation of design optimizations in downhole tools, drillstrings, rig capability, and drilling fluid to improve ROP in slimholes. Completion design optimizations are also implemented for slimmer holes to avoid any significant loss in stimulation effectiveness and maintain well value.

Bottomhole-pressure changes because of drillstring movement, referred to as “surge-and-swab”, were earlier acknowledged as a problem during drilling. In offshore drilling, there is another source of drillstring movement: vertical movement of floaters induced by ocean waves and swell, referred to as “rig heave.” Downhole chocking was introduced as a method to reduce downhole pressure oscillations induced by the rig heave. Verification of Downhole Choke Technology in a Simulator Using Data from a North Sea Well provides an overview of the surge-and-swab computer simulator, its capabilities, and limitations. The authors point out that the surge-and-swab simulation software is accurate enough to be suitable for investigating the effects of various measures to reduce surge and swab. 

High temperatures and wellbore-integrity issues are often encountered when drilling onshore and offshore wells. A Survey of Field Experiences With Formate Drilling Fluid presents worldwide implementations of formate drilling fluid, including field cases in Canada, the North Sea, Germany, the Middle East, and Russia. Experiences with formate mud in Chinese fields that were previously unknown because of the language barrier are also reported. Most field cases reported high ROP, excellent wellbore stability, good thermal stability, and high production rates upon completion. Reclamation and reuse of formate have significantly improved the cost-effectiveness of formate mud. According to the survey, formate mud is one of the best choices for drilling high-temperature wells, troublesome formations, and long horizontal wells.

The blowout-preventer (BOP) is a critical well-control safety barrier used during drilling and completion operations. Model-Based Health Monitoring of Annular Blowout Preventers presents an adaptive model-based approach for the real-time condition and health monitoring of annular BOP functions. The proposed model is adapted using simulated and in-field annular closing-event test data. The identified model coefficients are then monitored to detect, isolate, and estimate annular preventer degradation, faults, and failures.

That’s it for the fourth issue in 2019. If you have any suggestions to make our journal become better, please e-mail me at Shilin.Chen@Halliburton.com. Your opinions will be seriously considered.

Shilin Chen, SPE Drill & Compl Executive Editor,
Chief Technical Advisor, Halliburton