External Acoustic Sensors and Instruments for the Detection of Sand in Oil and Gas Wells

Abstract

Abstract From the earliest days of oil and gas production, solids mixed with the flowing medum have caused problems. The origins of these solids (sand) can be attributed to formation particles, solids introduced into the well such as drilling mud and frac sand, corrosion products (metal loss) and any other solids flowing through a system. With the ever changing methods of well drilling and completion the probability of sand is much higher today. In addition, the financial payback time is shorter so that more flow must be attained in a quicker and shorter time frame. If the production of sand is not minimized, formation damage can occur, downhole well equipment can be damaged, surface production equipment can be damaged and plugging of surface equipment can occur. The damage to the equipment alone can be expensive as well as the loss of product during downtime. In addition, the possibility of failures due to sand erosion can be catastrophic as produced fluids and gases can escape into the land, sea or atmosphere when a failure occurs due to erosion. There are many methods of sand control. In order to control the sand production it is necessary to have an early indication of the sand flow and its intensity. This paper will give a brief overview of the history of sand monitoring and the latest technology available for the detection of sand and the detection of the damage (erosion) that sand can cause. Introduction In the production of oil and gas a borehole is drilled through to a strata of rock that has enough porosity to allow the flow of liquids and gases from the rock into the borehole. This liquid or gas, or combination of liquid and gas, then flows, or is pumped up, through the borehole to the surface. Solids mixed in with the produced fluids and gases indicate that either the formation is breaking down or other solids such as fractionation solids, drilling mud, construction debris, scale, or corrosion products are flowing up the well bore. In any case this flow of sand is undesirable. Breakdown of the formation can lead to unstable flow and formation damage that can eventually lead to loss of production and even abandonment of the well. When other solids are flowing with the product we usually see an initial heavy flow of solids in a new well as these solids introduced as a result of drilling, formation fracturing, cementing, and production completion construction that have accumulated in the well bore flow to the surface. Once the initial amount of solids are clean from the well, the flow of solids is usually stabilized until such time as the well is adjusted to flow at such a high rate that the solids from the formation (sands) break loose and flow up the well bore. In addition, after a period of time produced scales and corrosion products can also flow to the surface.