Innovative Hydraulic Isolation Material Preserves Well Integrity

Abstract

Annular fluid or gas migration, resulting in surface hydrocarbon leaks or sustained casing pressure (SCP), is a problem operators face worldwide. With energy demands escalating, it becomes increasingly important to maintain production from existing wells and bring new wells on line without delay. Internal company policies regarding health, safety and environment, along with increased government scrutiny of the petroleum industry, can require wells to be shut-in if leaks or SCP are present. Estimates of the number of leaking wells have varied widely as reporting standards have evolved over time and from country-to-country. In Western Canada, however, there are detailed reports of over 18,000 wells having Surface Casing Vent Flow (SCVF) that in some cases requires them to be shut in and production suspended. From spud-in to abandonment, an oil well is subjected to numerous, repeated events that could compromise zonal isolation. Resulting damage, in the form of cracks in the isolation material or the creation of a microannulus, can allow hydrocarbons to flow to surface or become trapped below the wellhead. This paper will describe a novel zonal isolation material that responds to a loss of hydraulic isolation. If hydrocarbon flows occur within or around the primary cement sheath, the material will seal these flows and re-establish well integrity. The system, which has slurry properties comparable to standard oilfield cements, is designed to be pumped as part of any primary cementing operation on wells drilled with water or oil-based drilling fluids. This material was used in well construction operations for wells drilled in Eastern Alberta, and can be applied to reduce the incidents of SCVF in this area. This ability of this system to eliminate hydrocarbon flows has been confirmed with high-pressure laboratory testing, and it has been successfully field tested in Western Alberta. Introduction As worldwide demand for petroleum continues to increase, operators face the challenges not only of finding new reserves of oil and gas, but also of maximizing the productivity and longevity of the wells that are drilled into existing reservoirs. According to the International Energy Agency (Oil Market Report 2007; Press Release 2006), worldwide petroleum demand is expected to increase by 13.9 million BOPD, from the current level of 85.9 million BOPD to 99.5 million BOPD, over the next seven years. By contrast, production has increased by only 6.7 million BOPD over the last seven years (Short-Term Energy Outlook 2007). If the industry is to keep pace with this demand, operators will have to look at ways to maximize returns from individual wells, in addition to improving overall reservoir recovery. Great advances have been made in cementing practices over the years. These advances include improvements in fluid displacement modeling as well as the development of slurries with improved chemical and rheological properties. These advances have gone a long way towards improving hydraulic isolation, but they do not address damage to the cement sheath that may occur days, months or years after the cement has set. This potential for loss of hydraulic isolation during or after a well's productive life represents a weak link in hydraulic isolation. A damaged cement sheath can allow the migration of hydrocarbons, which can reach the wellhead in the form of sustained casing pressure (SCP) or surface casing vent flows (SCVF), potentially requiring a well to be shut-in, repaired or abandoned prior to the end of its productive life.

Review of studies on plugging compositions creation with controlled rheological properties and the ability to restore fluidity for completion, workover and abandonment of oil and gas wells

“…В работах исследовательского коллектива нескольких лабораторий под руководством P. Cavanagh [28,29] описывается новый подход к изоляции и герметизации скважин за счет активизации самовосстанавливающихся компонентов цемента (их набухания) в присутствии потока углеводородов при возникновении проблемы целостности цементной матрицы. После активации подобных процессов при контакте с углеводородами поврежденная зона закупоривается и может быть снова регенерирована в случае повторного или дальнейшего повреждения.…”

“…Модифицированный цемент, помимо самих самовосстанавливающихся добавок, может содержать и обычные добавки, такие как диспергатор, пеногаситель, замедлитель схватывания, агент для контроля водоотдачи и добавку для контроля миграции газа. Плотность суспензии может легко регулироваться, она охватывает диапазон от 1440 кг/м 3 до 2150 кг/м 3 , а диапазон рабочих температур варьируется от 20 °C до 138 °C [28,29].…”

“…В ряде проведенных лабораторных испытаний P. Cavanagh, J. Roth и др. [28,29] были получены следующие характеристики самовосстанавливающихся цементов. Так, модифицированные восстанавливающиеся составы имеют механические свойства, эквивалентные классическим цементным системам.…”

Use of Novel Self-Healing Materials to Control Sustained Casing Pressure and Prevent Long Term Environmental Impact

“…Reaction rate and degree of swelling will depend on the swelling material concentration and on well conditions such as temperature, pressure and the type of hydrocarbon to which it is exposed. This system has been used successfully on multiple underground gas storage wells drilled in Northern Italy, and documented in SPE paper 110523 3 .…”

The potential of using micro-sized crosslinked polymer gel to remediate water leakage in cement sheaths

“…However, cement squeeze cannot be used effectively to mitigate and prevent leakage because of low cement injectivity, pressure restriction, pinhole leakage, micro-channels and fractures inside the leaking formation, and micro-cracks within primary cement (Jones et al 2014). To overcome these limitations, self-healing cement was developed (Cavanagh et al 2007;Roth et al 2008;Reddy et al 2010;Khatri 2013). Self-healing cement enables an automatic repair when micro-annuli, an internal cement crack, or another flow path is created.…”