Abstract
Sand cleanout is operated by circulating a liquid or a multi-phase fluid into
the wellbore to bring sand particles to the surface. Although the sand cleanout
operations have been applied successfully in most wells with high efficiency
and negligible leakage, failure of effective sand removal always occurs in low
pressure wells and absorption wells due to heavy loss of circulation. To make
the matters worse, solids in the bottomhole may even flow back into the
formation to cause further formation damage around the wellbore. In this paper,
an integrated sand cleanout system has been developed to effectively remove
loose sand particles in low pressure wells and absorption wells by employing a
jet pump. More specifically, a high pressure working fluid is pumped through
the annulus from the surface and then divided into two parts. One part of the
fluid is diverted as the sand carrier fluid to flow downwards, stir up the sand
particles via a jetting nozzle at the bottom of a sand cleanout pipe, bring the
loose sand particles upwards and then to be boosted by using a jet pump. The
other part of the fluid acts as the power fluid of the jet pump to reduce the
bottomhole pressure so that the carrier fluid, together with the sand
particles, will be sucked into the pump and then lifted to the surface.
Detailed structure and principle of the integrated sand cleanout system are
described, while a theoretical model is formulated to optimally design the
system based on the experimental data and jet pumping theory. It has been shown
from field applications that the integrated sand cleanout system makes
significant improvements in achieving high efficiency and preventing leakage in
low pressure wells and absorption wells.
Introduction
Increasing interest and efforts have been focused on sand cleanout in the
upstream oil and gas industry since the 1960s(1). Although 60% of
the oil and gas reserves are discovered in carbonate reservoirs, approximately
90% of the world's oil and gas wells are drilled in sandstone reservoirs, among
which 25-35% of the wells experience a certain degree of sand production during
the life of the well(2). In principle, sand particles are dragged by
the formation fluids, carried out from the formation and settled down at the
bottom of the well. By the time the casing is full of the sedimentary solids,
the pay zone becomes plugged and the downhole pump gets stuck. Workover
activities have to be carried out for reviving the well to bring it back into
production(3). Frequently, removal of wellbore fill is considered
inadequate, leaving large quantities of fill material (e.g. sand particles) in
the well, which often requires repeating well cleanouts in a relatively short
time interval. In addition, wellbore cleanouts are extremely time-consuming,
preventing timely return of wells to production and increasing the cost of well
maintenance(4). Therefore, extensive research efforts have been made
to develop: 1) cleanout equipment, such as the concentric pipe, tubing-operated
pump-to-surface bailer and coiled tubing with jetting nozzles(5,
6);
© 2009. Petroleum Society of Canada (now Society of Petroleum Engineers)
View full textPDF
(
1,287 KB
)
History
- Original manuscript received:
26 March 2007
- Meeting paper published:
12 June 2007
- Revised manuscript received:
27 January 2009
- Manuscript approved:
4 April 2009
View Cart
