In the 1940's experimental fracture treatments were performed without proppant. However in most formations unpropped fractures heal quickly with no sustained benefit, and in 1947 river sand was introduced as proppant. The first evolution in proppants came in the 1950's, when river sands started to be replaced by higher quality mined sands from Illinois and Texas. This was the early recognition that employing more uniform, rounder, stronger -and ultimately more conductive proppantproduced larger production gains. From this point on efforts concentrated on improving sand performance and finding new propping materials that could cope with harsher conditions. In the 1960's, petroleum engineers incorporated walnut hulls, glass and plastic beads into frac designs. The 1970's saw the introduction of resin coated proppants and the first commercial bauxite based ceramic proppant, followed by low and intermediate density ceramics in the 1980's. However, throughout this time, proppants still served one primary purpose -to prop open the fractures and provide a conductive flowpath for hydrocarbon production.Placement of proppant deep into the formation brings a unique opportunity of conveying new functions, additional to the primary roles of keeping the frac mechanically open and providing a conductive path for production enhancement. For decades most proppant development efforts concentrated on developing proppants that could either cope with higher stress and deliver higher conductivity or improve proppant transport via lower density, while minimal effort was put in adding other functionalities. Recently it has been recognized that other functions can be incorporated into manmade proppants during the industrial manufacturing process, thereby exploiting the placement opportunity. These functions might include assuring flow in the production system, providing reservoir surveillance or monitoring fracture properties. This paper will review the latest technology developments that enable the incorporation of these functions into proppants, including how the new proppant delivered technologies permit users to cost effectively deploy additional functionalities in the initial completion of hydraulically fractured, frac-packed and gravel-packed wells. The paper will also present recent case histories of field implementations of these technologies which illustrate how these high function proppants can reduce overall operating costs, enhance production and diagnose hydraulic fractures.
Halite scale is a wide spread problem throughout several basins in the United States. This scale can form in surface equipment, downhole tubulars as well as affecting production. Traditional remediation of halite can be accomplished by dissolving the scale in fresh water as well as recycled water. In most cases the operator must factor in the cost of fresh water, trucking, manpower, anti-scale additives, and disposal of additional produced water. These treatments are often frequent with multiple applications per week. The approach described in this paper will prevent the formation of halite scale for a given period of time. This is accomplished through the use of a new porous ceramic proppant-based chemical delivery system in which a halite inhibitor is infused. The infused halite inhibitor is encapsulated with a semi-permeable membrane to regulate the elution rate of the inhibitor from the porous proppant carrier. The chemical delivery system is added to the bulk proppant as a small weight percentage of the bulk proppant and is placed in the fracture as normal proppant. Several wells in the multiple basins for several E&P companies were completed using this new chemical delivery system, which allowed for a significant amount of halite inhibitor to be placed within the proppant pack. As fluids flowed over the proppant pack the halite inhibitor was slowly released. This paper intends to describe the mechanism for which the inhibitor acts, the control release mechanism of the substrate and the engineering behind the placement and volumes of the halite infused proppant. This paper will also discuss the data collected from laboratory modeling and the implementation of these products in fracturing applications. The use of this chemical delivery system will allow these operators to defer remediation, lowering lease operating expenses. This paper will be useful to all production and completions engineers and technicians operating in an area with halite scale issues. This new chemical delivery system allows for deferred implementation of traditional remediation strategies while extending the most productive time of the wells life. This halite inhibitor delivery system not only improves estimated ultimate recovery but also lowers lease operating expenses.
Production of hydrocarbons in deep water reservoirs involves the economical flow of hydrocarbons from the reservoir to the point of sale. One important consideration is effectively preventing / handling solid deposits which can be both organic (i.e. paraffin, asphaltenes) and inorganic (i.e. calcite, barite, halite) in nature. These deposits can cause catastrophic blockage in pipelines, subsea equipment and impair fracture conductivity and well performance. To prevent deposition and lost production inhibitor chemicals are typically delivered downhole via tubulars, injected at points along flow lines and risers and as an additive to fracturing fluids. Installing and maintaining such injection systems in these very challenging environments can be expensive to the operator of such facilities. A new delivery system has been developed which utilizes an infused and encapsulated ultra-high strength porous proppant (UHSPP). The stresses of these deep, high pressure reservoirs requires proppant that can resist closures up to 20,000 psi and previous attempts of using solid inhibitors in these environments have typically sacrificed conductivity. The use of this UHSPP does not negatively impact conductivity and allows for delivery of inhibitors in previously unreachable areas. The delivery system allows inhibitor chemicals to be released at a slow, controlled rate when the proppant comes in contact with produced fluids and results in a highly efficient, reservoir based chemical delivery system. Typical treatments are designed to last for years of production. This paper will present a case study of the use of this new technology in owery tertiary wells in the Gulf of Mexico. These wells have been treated with an inorganic scale inhibitor using a multi-functional UHSPP. This paper will also describe how substrate type and pore structure can be engineered to maintain conductivity at very high closure stresses. It will also show how semi-permeable membranes can be tailored to specifically control the release of these inhibitors upon contact with production fluids. This paper will prove useful for all completion, production and facility engineers engaged in offshore operations, and can also be adapted similarly to onshore wells. The cost savings from utilizing a UHSPP delivered chemical system can provide a significant reduction in operating expenses.
Most North Slope Alaska oilfields undergo waterflood for pressure maintenance and improved oil recovery. Both recycled produced water, as well as treated seawater are injected into the reservoir which then mixes with connate water in the formation. The combination of seawater with connate water in the reservoir can lead to severe barium sulfate and calcium carbonate scaling in the production wells and reservoir. The scaling is particularly severe at initial breakthrough of the waterflood front in the production wells. However, since water breakthrough timing is unknown, most scale inhibition techniques commence after observing first water production, which is often too late. This scaling can cause significant production losses, leading either to costly remediation with acid, or in the case of barium sulfate, may be impossible to repair. A novel scale inhibition technology which uses scale-inhibitor infused proppant has been applied to mitigate scale in other North American oil and gas fields. Unlike the North Slope fields, most of these wells must be inhibited from first production to prevent scale formation from the start. The technology uses a novel process whereby scale inhibitor is only released when it comes in contact with water, making it a choice option for use in North Slope fields where scale inhibitor must be in place at waterflood breakthrough, which is typically unknown. One operator elected to install this technology in the Oooguruk field in Alaska. The Oooguruk field is an undersaturated oil reservoir found on Alaska's North Slope. Development includes both production and water injection wells, arranged in a line-drive pattern. Wells are drilled horizontally and completed with multistage hydraulic fracture treatments, which are designed to create longitudinal fractures along the wellbore. Water injection is initiated in the injectors immediately after post-frac flowback operations. Based on the severe scaling observed in other area fields, engineers deemed it imperative to put a plan in place to address scaling when waterflood breakthrough occurred. Since these are horizontal wells, scale remediation is difficult (if not impossible) to perform once the scaling damage has occurred. To address this problem, the novel scale inhibitor proppant technology was incorporated in the hydraulic fracture treatments of the producers. Four wells employing these treatments were successfully completed in 2015 and 2016. Testing of the water during the fracture clean-up period showed inhibitor returns as expected, tailing off as the load water was produced. In early 2018, the first waterflood breakthrough occurred on several wells, and the produced water was analyzed and found to contain inhibitor levels above the minimum designed inhibitor concentration, thereby successfully providing immediate scale inhibition to the entire wellbore. This paper will review the proppant delivered scale inhibitor technology, document the field application including the project analysis and design, and present the inhibitor results. This is the first installation on the North Slope of a scale inhibitor technology that can effectively remain dormant, and successfully inhibit scale upon waterflood breakthrough years later. In this case history, the scale inhibitor proppant is inhibiting water that did not break through until 2-3 years after placement. This paper will be beneficial to completions and production engineers who wish to prevent the detrimental effects of scale in their production wells, particularly in waterflood operations.
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