A novel alkali-surfactant for optimization of filtercake removal in oil–gas well

The main objective of this study is to improve the oil-based filtercake removal at the wellbore second interface through chemical method. The reductions in near-well permeability, bonding strength at wellbore second interface and acidizing treatment are the critical problems in oilfield upstream operations. One of the major causes has been identified as drilling fluid filtrate invasion during the drilling operations. This as result leads to near-well reduction in-flow capacity due to high drawdown pressure and wellbore instability. A number of chemical methods such as enzymes, acids, oxidizers, or their hybrids, have been used, however, due to the presence of a number of factors prior to its removal, there are still many challenges in cleaning oil-based filtercake from the wellbore surface. There is a need for development an effective method for improving oil-based filtercake removal. This study presents a novel Alkali-Surfactant (KV-MA) solution developed in the laboratory to optimize the filtercake removal of oil–gas wellbore. The Reynold number for KV-MA solution was found to be 9,068 indicating that turbulent flow regime will dominate in the annulus which enhances the cleaning efficiency. The wettability test established that, contact angle of 14° was a proper wetting agent. The calculated cleaning efficiency was 86.9%, indicating that it can effectively remove the oil-based filtercake. NaOH reacts with the polar components in the oil phase of the oil-based filtercake to produce ionized surface-active species; hence reducing the Interfacial Tension. Surfactant quickens the diffusion of ionized species from the interface to the bulk phase.

Alternative Use of Achi, UKPO, and OFOR as Substitute to Standard Viscosifier

In Nigeria, drilling companies import a bulk of drilling fluid materials that they use to carry out their respective operations. This has been a major concern to oil and gas industries since these drilling fluid materials cannot be recycled, are highly expensive in terms of foreign exchange, are not environmentally friendly, not very effective, and non-biodegradable. This work presents an experimental investigation into the reliability of the use of local materials as a substitute to conventional viscosifiers. Local materials used in the analysis are Mucuna solannie (Ukpo), Brachystegia eurycoma (Achi), and Detarium microcarpium (Ofo). The results obtained from the experimental analysis show that they compared closely to the standard viscosifer formulated with Pac-R. The results showed that the density, specific gravity, pH, yield stress, Gel strength, Plastic Viscosity, and yield point of mud formulated from local materials compared favorably with that of the imported viscosifer. It was observed that an increase in concentration produced a better result. Hence, they could replace the Pac-R considering cost, cutting carrying ability, etc.

The Use of Hydraulic Completion Snubbing Units HCU in Long Laterals in U.S. Shale Plays

Coiled tubing units (CTU) have been used to drill-out frac plugs in shorter horizontal shale wells for the last decade, but coil has mechanical limitations. The new innovative technology of Hydraulic Completion Snubbing Units (HCU) is gaining popularity across North and South America to drill-out frac plugs in long lateral, high-pressure, and multi-well pads. The HCU is designed for drill-outs and interventions where coil may not be the best option. This paper will summarize the recent evolution of the HCU system. Case histories will be provided from the Appalachian and Permian shale plays. The latest HCU consists of a stand-alone unit that mounts on the wellhead after completion. The primary components include the jack assembly, a gin pole, traveling/stationary slips, a redundant series of primary/secondary blowout preventers, a rotary table, power tongs, and an equalize/bleed off loop. Tubing up to 5 ½" is used to carry a downhole motor, dual back pressure values, and the drill bit. Slickwater is used for the drilling fluid to carry out parts from the frac plugs while the tubing is rotated via the jack rotary table. Torque and drag modeling are performed to guide downhole expectations that allow most wells to be drilled in one trip and with one bit without short trips back to the heel or bottom- hole vibration assembly tools. Finally, a remote telemetry data acquisition system has been added that summarizes the drilling data and key performance indicators. In 2016, a North American operator drilled and completed the first super lateral in the Appalachian Basin, setting the completed lateral record at over 18,500 ft. Since then, many operators have been routinely drilling laterals between 12,000 ft and 16,000 ft. HCU technology has been used in the longest laterals in onshore North America, including the lower 48 U.S records for completed lateral length (LL) at 20,800 ft and the total measured depth (MD) record at 30,677 ft. The average lateral contains between 60 to 90 plugs and can be drilled out in 3.5 to 4.5 days. The record number of plugs drilled out by an HCU is 144 and took 5.2 days. High-pressure wells are also routinely encountered where pressures range from 3000 to 8000 psi during operations. Operators are achieving faster drilling times per plug, less chemical usage, faster moves between wells, and running tubing immediately after the drill-out, thus eliminating the need for a service rig. Operator's desire to reach total depth with the least risk and as cost-efficiently as possible resulted in the HCU gaining market acceptance. This paper will showcase the novel evolution of the HCU system that has enabled it to be a safe and effective option for interventions outside of just frac plug drill-outs such as fishing for stuck/parted coil or wireline and installing production tubing/artificial lift systems.

Modified Corn Starch as an Environmentally Friendly Rheology Enhancer and Fluid Loss Reducer for Water-Based Drilling Mud

Summary Drilling fluid rheology and fluid loss property are fundamental parameters that dictate the effectiveness and easiness of a drilling operation. Maintaining these parameters under high temperatures is technically challenging and has been an exciting research area for the drilling industry. Nonetheless, the use of drilling mud additives, particularly synthetic polymers, threaten ecological environments. Herein, modified corn starch (MCS) was synthesized, characterized, and investigated as an environmentally friendly rheology enhancer and filtration loss controlling agent for water-based mud (WBM) at high temperatures. The experimental results indicated that MCS exhibits better performance in improving rheological properties and fluid loss controlling ability for WBM than the commonly used mud additives. With the addition of an optimal concentration (0.3 wt%), MCS improved the rheology and fluid loss behavior of WBM formulation at harsh aging temperature (220°C) by practically 4 times and 1.7 times, respectively. The MCS was revealed to perform superbly over polyanionic cellulose (PAC) addition at all investigated temperatures. The better performance of the MCS was ascribed to the improved entanglements in the mud system owing to the additional hydroxyl (OH) groups. Besides, the Herschel-Bulkley model was found to be a constitutive model that described the rheological properties of the investigated muds satisfactorily. Moreover, the MCS was found to exhibit acceptable biodegradability properties.