The criteria for success of any primary cementing job is achieving permanent zonal isolation. Incomplete mud removal will affect the zonal isolation in several different ways and may lead to the development of a communication channel in the annulus and subsequently jeopardize the well integrity. Nonaqueous fluids (NAF) are incompatible with cement slurries; the quality of the cement placement and set properties will be strongly affected by the presence of the NAF residue down hole. Although this problem can be mitigated through the addition of various chemicals providing compatibility, mud-thinning, reduction of the interfacial tension, and water-wetting functions, the current surfactants and solvents on the market have limited application in terms of temperature and type of drilling fluids. In addition, the current API/ISO testing protocols are generic and results are not reproducible. Recently, improved laboratory procedures have been proposed and these improved experimental methods were used on more than 200 surfactants and solvents. A screening process helped in selecting the optimum chemistry as a function of the conditions (type of base oil, salinity, temperature). This enabled developing design guidelines to select an optimized tensioactive package comprising a limited number of chemicals, from which field users would select the ones to combine for their applications. The new tensioactive package was used successfully in two field trial wells in the 7-in. liner sections in a mature development field offshore Thailand. After a thorough comparison between the currently used package and the new one, the laboratory results using the field mud show superior cleaning results and efficiency with the new chemical package. The zonal isolation was confirmed using an ultrasonic imager logging tool. After the two successful field trials, the tensioactive package was selected as the spacer of choice for a critical new development field campaign offshore Thailand in which zonal isolation between production zones was critical for selective production from each of the zones separately. This paper will describe the newly improved laboratory methodology and selection criteria of the new tensioactive products and provide a detailed case history of the application in the development campaign, including the design, execution and evaluation of the job.
Technology Update An efficient removal of drilling fluid is essential to successful cementing operations. When a cement slurry comes into contact with mud residue, the cement may not set properly or adhere to the casing and formation, thereby preventing the isolation of permeable zones under different pressure regimes. This can cause stimulation out of zone, production of unwanted fluids because of communication between zones, loss of hydrocarbons into lower-pressure formations, corrosion of casing, and blowouts. In recent years, the industry has focused considerable attention on enhancing cementing practices to ensure well integrity and zonal isolation. To clean all well surfaces after the placement of casing, an intermediate water-based fluid, or spacer, is pumped between the drilling fluid and cement slurry. Typically, a package of surfactants or solvents is added to the spacer to improve cleaning and displacement efficiency. However, over the past decade, spacer formulations have not evolved as rapidly as the chemistry of drilling fluids. Every year, operators drill deeper, more complex, and higher-temperature wells under a growing range of downhole conditions. To boost performance, drilling fluids incorporate a greater variety of nonaqueous fluids (NAFs) based on synthetic and natural oils—mineral, paraffinic, and olefinic oils—with much longer carbon chains than traditional diesel-based muds. As such, NAFs are much more difficult to clean. Although spacers are intended to separate drilling fluid from cement, a small amount of spacer fluid—from 5% to 10%—typically contaminates a portion of the cement slurry. Many spacer chemistries affect cement properties, such as thickening time, rheology, and compressive strength, often precisely where zonal isolation is most essential. If the cement has not fully hardened by the time a cement bond log is run, it may not show up clearly and the top of cement (TOC) may be uncertain. Therefore, it is vital to ensure that spacers remove the maximum amount of mud while having a minimal effect on cement properties. Since NAF compositions vary widely, there are no universal spacer formulations. Most are designed and tested on a case-by-case basis using procedures that differ from one operator or location to another. Existing American Petroleum Institute (API) recommended tests for evaluating the suitability of a particular spacer have been found nonrepeatable. In addition, no test protocols exist for well conditions above 85°C, despite the large number of cement jobs in wells with bottomhole temperatures of up to 150°C. Along with salinity and the type of drilling fluid, temperature is one of the most critical factors influencing cement integrity. Thus, enhanced test procedures and spacer formulations are needed.
The Jasmine Field began production in 2005 with initial estimated recoverable reserves of 7 MMbbls.
Oil Production in Gulf of Thailand Offshore has always been hijacked by high water-cut. Field recovery suffers with most sand RF<10% due to premature water breakthrough and by-passed oil. Connecting sand pockets of varying sand quality and huge heterogeneity contrast for commingled inflow has further worsened non balanced production, especially in the progressive development towards horizontal wells' production. However, the deployment of downhole flow control (ICD) in Field-BY as pilot, has revolutionised conventional surface-choke controlled production towards downhole nozzles' inflow and drawdown control. The ICD's pilot, BY-A is selected based on its strategic comparison-value to an existing horizontal well, i.e. BY-B, completed with sand-screen standalone, SAS in the same sand and about the same horizontal length. An 'apples-toapples' evaluation comparison over the same production time-lapse between ICD-case and the SAS base-case post-job production demonstrated that the ICD's pilot has prevailed in many production factors and completions strategy as such:i.ICD's well BY-A with ~2 months delay of water breakthrough, unlike BY-B of instantaneous water breakthrough with 40% water-cut in the same period.ii. BY-A has produced >50,000 barrels more oil than that of BY-B for the first 7-months iii. ICD's application has freed up conventional surface choking-back control upon breakthrough. Instead, more liquid rates are pumped at controlled water-cut that transformed previous production to more rates with more oils.iv. ICD's design and modeling, updated with LWD-derived data near real-time, has optimised the completions cost. Effectively, lower ICD's screen completions are applied only at sand-contact.In brief, the entire ICD's design and support together with the post-job production monitoring and optimisation will be discussed. This work provides an insight into transforming an otherwise ordinary horizontal well with typical high water-cut constraints into one of the guiding successful ICD's well that has warranted more ICD's application in the operators other nearby field developments. Field Introduction and Production ChallengesField-BY is located in Block 5/27 offshore Gulf of Thailand, on the northern flank of the Pattani Basin as shown in Figure 1. It is operated by Mubadala Petroleum (Thailand). In most reservoirs, the shallower sands are fluvial channels while the deeper layers are lacustrine deposits. The resulting reservoir geometries are complex in lateral extent and vertical heterogeneity intertwined with shoreface, stacked and extended channels and/or individual channeled sand pockets, for example the targeted TX 75083-3836, U.S.A., fax +1-972-952-9435
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.
customersupport@researchsolutions.com
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.