Abstract We present a comprehensive wellbore cleanup toolbox, which combines and optimizes the benefits of jetting, milling and chemical dissolution techniques. The system will clear obstructions from the wellbore and clean back to the tubing wall in a safe non damaging manner.
Conventional cleanup techniques use wash tools, which are inefficient, solvent bullheading which is poorly targeted and wastes reagents or milling tools which can be damaging to the wellbore. These present a less than optimized solution to a commenly occurring problem.
We have developed a tool box which includes an optimized jetting tool for cleaning out soft and weakly consolidated materials. It also presents benefits when used with solvents, or chemical reagents by delivering the fluids directly into the blocking or plugging obstructions with sufficient energy to accelerate the dissolution process and minimize the fluid consumption.
For insoluble materials with a clearance hole we use a self powered jetting tool with the non damaging, Sterling Beads, abrasive system. This will remove scale or other obstructions from the well without damage to the wellbore or jewelry.
For hard and insoluble bridges or plugged wellbores we use a hybrid jetting and milling system. Using a modified PDM with a radial jetting head and small PDC mill. The mill is sized to be smaller than the tool so it cannot contact the tubing or jewelry. Hence the system is safe and non damaging. In addition by using a smaller mill the drilling torque is reduced and the system is more reliable than an equivalent conventional system.
Introduction We consider the removal of obstructions, scale growth and plugging from production tubulars, jewelry, screens and perforations. Matching the solution to the problem is critical here. So, first we characterize the obstruction types.
We review existing cleanout techniques, considering wash tools, solvents and mechanical systems, considering the strengths and weaknesses of each of the systems.
We then discuss the new solution to each of the cleanout problems, together with case studies describing the system performance.
Problem definition The solution to an obstructed wellbore is dependent on the type and condition of the obstructing material as well as the geometry and condition of the well and the sensitivity of the well to fluids which could be used for the workover.
Broadly the obstructions can be divided into several groups:
Unconsolidated fill. Typically formation sand produced from the reservoir, frac sand left in the wellbore including sand or flour left in the wellbore for zonal isolation or pressure isolation purposes.
Cemented but Soluble solids. These include soluble scales, typically Calcium Carbonate, as well as soluble cements. We also consider the harder aspheltenes in this category.
Insoluble obstructions which do not bridge the well. Most forms of insoluble scale are included here, but not the situations where the scale has been allowed to grow over the entire wellbore.
Insoluble obstructions which bridge the well. Cement plugs, solid scale and all other mineral growth.