With the development of the petroleum industry, the drilling field is expanding,
the application of asphalt modification products in drilling is getting more and more
attention. Asphalt is composed of a small amount of hydrocarbon compounds and a
large amount of non-hydrocarbon compounds. Asphalt is generally divided into two
main categories:
Petroleum asphalt and natural asphalt. In oil drilling is widely used in asphalt
modified products, asphalt modified products are divided into two broad categories;
that is, modified colloidal asphalt and modified dry powder asphalt.Our modified
asphalt is mainly modified dry powder asphalt. Modified asphalt or petroleum
modified asphalt (emulsified asphalt, oxidized asphalt, sulfonated asphalt, cationic
latex asphalt, etc.).
Modified asphalt is moderately soluble and dispersible in the The dissolved
portion improves the lubricity of the drilling fluid, while the dispersed portion,
together with the other treatments in the drilling fluid, effectively adheres to the
well wall, forming a dense layer of mud cake and a film of oil on the wall, which
reduces the friction of the drilling tools on the wall and also reduces the chunks that
will fall off when the drilling tools collide with the well wall.
Asphaltenes are extremely effective in blocking the microcracks in the formation,
preventing the penetration of drilling fluid and filtrate from the microcracks,
preventing the well from caving in, and protecting the oil formation. Therefore,
asphaltenes are extremely effective anti-collapse agents and formation protectors for
oil drilling.
■ Oil-based drilling fluid plugging water loss reduction agent with asphalt is
oxidized asphalt.
■ Play a unique role, is through its adsorption of strong pickled in the clay
particles and shale surface, preventing the hydration of clay particles dispersion, the
formation of water-repellent oil film, reducing the contact between the shale and
water, effectively protect the drilling fluid rubber protection, in order to achieve the
protection of clay particles, inhibit the hydration of the shale, blocking the shale
cracks and conglomerate gaps, so as to play a role in reducing the amount of filtration
loss of the drilling fluid and the stabilization of the well wall.
■ Because the main components of asphalt and gum, their role in the drilling fluid
is to moderate dissolution and dispersion, asphalt can improve the viscosity of the
drilling fluid, gum can seal the mud cake microporous holes to reduce the filtration
loss. At the same time, after dissolution and dispersion of asphalt, it can work
effectively with clay or bentonite to keep the drilling fluid with good viscosity and
cuttings, coupled with the effective use of emulsifiers, it can also be a better effect of
asphalt. Because, the effective content of oxidized asphalt bitumen is more than 60%.
- Selection of asphalt softening point according to downhole temperature
The softening point of oxidized asphalt is an important indicator of the use of
asphalt,. Generally, the softening point of asphalt is selected based on the well
temperature.Selecting different asphalt for high and low well temperatures,
softening point of asphalt can only be effective controled.Otherwise, high well
temperature selection of low softening point products, oxidized asphalt in the well
all dissolved, it will be difficult to achieve in the well plugging pores and cracks;
low well temperature selection of high softening point asphalt, so that the
particles can not be deformed plugging holes, and even through the vibration
sieve may be screened off.
- The drilling fluid creates a certain pressure on the well wall, squeezing the
deformed but not completely softened product into the well wall between , the size
of the microcracks is unpredictable. Oxidized asphalt particles can only be ground
to a maximum of 300 mesh, in the shimmering state is an irregular pattern, not easy
to squeeze into the microcracks. Therefore, the softening point of the oxidized
asphalt particles is the key point.
- When drilling a well, the temperature of the well increases gradually, so
different products are needed. Softening point is an average softening point at
different temperatures. The product is a mixture of petroleum asphalt and natural
asphalt after special oxidizing treatment. The softening point is actually a range of
values, where the length of the carbon chains in the natural asphalt and the
downhole environment are approximately the same within a certain range.
- Under different formation temperatures, the products are in different states,
and the softening point range should be matched with the temperature of the
formation. Assuming that the well temperature is 120 ℃, the softening point of the
product ranges from 60 to 120℃. If you prepare materials with different softening
points for adjustment on site, it is more troublesome to operate and difficult to
manage the logistics.
Therefore, we designed 4 types of oxidized asphalt with different softening
point ranges:
- Oxidized asphalt particles below 2mm can be used as oil-based drilling
fluid plugging agent. Partially dissolved in oil, both colloidal and particulate,
good plugging effect, to avoid plugging agent directly plugging the drilling equipment.
