17. Перечислите свойства раствора для крс на глинистой основе

Clay base mud

Profits

• Low costs

• Readily available

• High suspension capability and solids

carrying capacity

Constraints

• Clay swelling

• Formation plugging

• Water block and emulsion block

• Degradability over time

18. Расскажите о применении гибких нкт (coil tubing) при ремонте скважин

Use

• It is mainly used in operations that require a circulation inside the well, such as well killing, washing, acid jobs, lifting, cement plugs and others.

• Recently, due to the large diameters available, the coiled tubing is also used to carry out

final completions or to rectify completions that have become inadequate. This solution is

much more cost-effective than the operations with a rig.

Advantages

• Possibility of completing the well and carrying out workover operations without the use of the drilling/workover rig.

• High mob/demob speed towards workover rigs.

• Reduction of size of the required area towards workover rigs.

• High run in hole /pull out speed towards workover rigs.

• Possibility of carrying out underbalanced workover operations without killing the well.

19. Какие основные типы пакеров вы знаете

Production packers can be classified into two groups:

• Retrievable

• Permanent.

Permanent packers

Permanent packers can be removed from the wellbore only by milling. The retrievable packer may or may not be resettable, but removal from the wellbore normally does not require milling. Retrieval is usually accomplished by some form of tubing manipulation. This may necessitate rotation or require pulling tension on the tubing string.

The permanent packer is fairly simple and generally offers higher performance in both temperature and pressure ratings than does the retrievable packer. In most instances, it has a smaller outside diameter (OD), offering greater running clearance inside the casing string than do retrievable packers. The smaller OD and the compact design of the permanent packer help the tool negotiate through tight spots and deviations in the wellbore. The permanent packer also offers the largest inside diameter (ID) to make it compatible with larger-diameter tubing strings and monobore completions.

Retrievable packers

The retrievable packer can be very basic for low pressure/low temperature (LP/LT) applications or very complex in high pressure/high temperature (HP/HT) applications. Because of this design complexity in high-end tools, a retrievable packer offering performance levels similar to those of a permanent packer will invariably cost more. However, the ease of removing the packer from the wellbore as well as features, such as resettability and being able to reuse the packer often, may outweigh the added cost.

20. Объясните функции и назначение скребков

The scraper is used for removing (scraping) mud cakes, cement build-up, drilling cuttings, rust, tool cuttings, etc. from the internal casing walls.

It must be used every time it is necessary to run in a packer or a bridge plug in the well, inasmuch as any scale deposits could cause blockage in the column when running in.

The most frequently used scrapers are as follows:

• Baker roto-vert mod. 'C' Scraper

• Security type Scraper

Baker Roto-Vert mod. 'C' Scraper

Components

• The Baker Roto-Vert mod. 'C' Scraper consists of a body with a top male connection and a bottom female connection.

• The body is equipped with 2 sets of three-blade scrapers (each set covers a 360-degree range).

• Each blade has grooves with a left-hand helical screw development which is pushed outwards by four springs.

Scraping action

The scraping action of the scraper can be achieved both

• with reciprocation of drillstring (vertical reciprocating motion)

• and with a rotating motion.

The maximum scraping action is achieved with reciprocation of drillstring.

Security type Scraper

Components

• The Security type scraper consists of a quadrangular cross section body with a top male

connection and a bottom female connection.

• There are 4 cutters on the body which are pushed outwards by special springs and set so as to cover a 360-degree range.

• Each cutter has a helical development blade profile that virtually has a cutting action on the existing obstructions.

Scraping action

• Cleaning is achieved with reciprocation action: it is not recommended for situations that entail rotating operations.

• In case of an open hole, do not let the tool come out of the shoe: the retraction may be quite difficult.

• When the blades are worn out, the cutter can be rotated by 180°in order to extend its life