Rotating Jet Technology Improves Stimulation Fluid Placement to Effectively Treat Horizontal and Gravel Packed Wells – Lab Model Tests and Global Results Are Reviewed

Abstract

Effective placement of stimulation fluids on horizontal, long interval and/or gravel-packed wells is critical for cost-efficient production enhancement. Successful case history work in 19991, using precision rotary jetting technology (R-Jet) on the end of coiled tubing (CT), demonstrated to the oil and gas industry that fluid placement is a key factor in removing near-wellbore damage and optimizing well stimulation treatments. This paper will review continued efforts relating to precision rotary jet technology including extensive laboratory tests using a full-scale gravel pack (GP) model. Tests were videotaped for further visual study. Established guidelines applying lab results, computer modeling, and field validation provide a well-engineered, non-damaging (low nozzle pressure) treatment for optimum stimulation performance. Proper damage identification coupled with skillful stimulation fluid design are important steps to a successful job and will be highlighted in the global R-Jet case histories. The data clearly shows that a highly effective method of placing stimulation fluids into a completion, such as sand control screens or slotted liners, is to use CT-conveyed, rotary speed-controlled, forward-angled radial jets. This technique yields 360° coverage of the treatment area, is more efficient than traditional bullheading and CT methods and allows reduced treatment volumes to be considered. It applies to a wide selection of completions including horizontal wells which can now be successfully stimulated at reasonable costs. Introduction Around the world there are tens of thousands of completions with screens and liners2 which could benefit from a reliable and cost-effective method for removing near-wellbore damage caused by drilling fluids, poor completion practices, fines migration and produced fluids. Very often a well begins producing with some form of damage (skin) caused by drilling (drill-in fluid filter cake) or completion damage (lost circulation material, perforating, dirty fluids). This skin will gradually increase over time as the screen/liner continue to collect migrating particulates (fines). Even if a sand control completion begins with no skin, there is an increased chance, due to the down-hole filter mechanism of a screen or liner, that fines, scale, organic deposits and/or drill-in fluid (DIF) filter cake will begin to plug the completion or GP proppant. There are inherent difficulties associated with trying to remove damage from the screen or liner, from the matrix of a GP or from perforation tunnels. Damage related to migrating fines is typically composed of either quartz particles (silica), silicates and alumino-silicates (clays and feldspars) or, more commonly, a combination of these. Scale, although most commonly deposited in up-hole tubulars, can also be found in the near-wellbore or screen area in the form of calcium carbonate, calcium sulphate or iron bearing scales (to name a few). Since downhole screens or liners often filter some of the described particles, these particulates tend to be much more concentrated in the near-wellbore or screen/liner area than in the formation. Damage associated with DIF (mostly on horizontal wells) is generally related to water-based, oil-based or synthetic oil-based mud comprised of polymers and particulates. These systems are extremely efficient in forming a thin DIF filter cake barrier to control mud losses to the formation and aid in drilling the well. Although efforts are made to minimize remaining DIF damage during the completion process, they often fall short, leaving damage that can be difficult to remove with conventional fluids or pumping techniques. The chemical formulations used to react with the various damage mechanisms have been previously reported in numerous papers1,3–7 and will be further investigated in this paper. Much of a well's damage acts as a downhole choke. Identifying the damage and properly designing the stimulation system to remove it is a painstaking process. However, even the best of fluids, improperly placed, are destined to fail. Major laboratory research on treatment fluid delivery methods and the use of controlled hydraulic energy to remove damage will be a central focus in this paper.

Oxygen-Free Acid-Stimulation in an Underground Gas Storage Well Completed With Prepacked Screens

“…To effectively test jetting efficiencies cavitation effects must be removed by performing the test under pressure. Case histories of screen cleaning with rotating jetting technology have previously been reported [3]. Figure 6 shows a picture of the cut screen after the test with the low impact rotating/ pulsating jetting tool.…”

“…The yard test with the different jet nozzles showed that the low impact rotating/pulsating jetting tool and the two jet nozzles were non-damaging to the screen and thus, based on this criterion, were suitable for use during the screen wash and stimulation treatment. To ensure coverage of the completion by the treatment fluids, the rotating tool was the preferred choice [3]. Additionally, the rotating/ pulsating jetting tool induces hydraulic vibrations created by the pulsating effects of the jets, which dislodge insoluble fines in the pre-packed screen, and could open pore space normally unaffected by chemical action of the treatment fluid.…”