Solids control / management check list

XI'AN, China - Aug. 18, 2016 - PRLog -- Solids control check list should be considered before drilling a well. The answers to these questions will assist in the proper selection sizing, and operation of a solids management system.

Well Parameters/Deepwater Considerations

Where will the well be drilled?

What is the objective (e.g., oil/gas, geothermal, reentry, etc.)?

What formations and geological features are expected?

What type of well (straight hole, directional, horizontal) will be drilled? What problems are anticipated?

Additional considerations are required when the hole location is in deep water. Among the first problems encountered drilling in waters of any appreciable depths is shallow formations insufficiently consolidated to support weight imposed by a riser annulus loaded with even a low weight drilling fluid and cuttings. Routinely such upper hole segments are drilled without a riser, using seawater as the drilling fluid with intermittent viscous flushes to assist cuttings removal. Returns simply spill out onto the seafloor. Some of these shallow formation (sands) hold gas or water under pressure that will flow into the well bore when formations are penetrated

Even when small in magnitude and of brief duration, these occurrences are correctly called blowouts, that is, uncontrolled flows of formation fluid into the well bore. Different approaches are taken in face of these shallow formation flows. A weighted fluid, sufficient to control the shallow formation pressure, can be spotted in the hole and casing run. Sometimes drilling proceeds to some depth below the problem formation before casing is run. Sometimes flow will cease as the formation bridges over or the pocket exhausts itself. http://www.aipusolidcontrol.com/html/products/solids-cont...

Two of nature's phenomena have combined to cause extensive occurrences of such shallow formation with deepwater flows in portions of the United States Gulf of Mexico. The currents of the Gulf Stream have created a sharp water depth drop off from the outer continental shelf to what is known as deepwater. In severe instances, water depths increase from 600 to 10,000 feet over just a few miles farther distance from shore. This regional current pattern has existed over geological ages whether worldwide seawater depths were rising or falling, the shoreline advancing or receding.

Over the same geological ages, massive deposits of sediment were made by the Mississippi River when it reached the open waters of the Gulf of Mexico. Water depth is an excellent classifier of sediment size. With fluctuations of seawater depth, an alternating deposition pattern has existed with nonporous silt deposited atop porous sand throughout the region. This deposition has often occurred at a pace at which subsidence due to increased weight of newer overlying sediments has transpired with only little consolidation of the formations.

As a result of the actions of the Gulf Stream and the Mississippi River, the Gulf of Mexico—particularly offshore Southeast Louisiana— has become known for shallow gas flows from unconsolidated formations in water depths where drilling with returns through a riser are not possible. Additionally, the magnitude of the two natural phenomena have combined such that these shallow formation with deepwater flows are not only more frequent, but also tend to be much, much larger.

Early attempts to drill these potentially large shallow formation flow zones were made using seawater and viscous flushes, with returns let to seafloor. However, the influx magnitude and force on the unconsolidated near surface formations often created craters so large that reentry, even with casing, was difficult if not impossible. Massive amounts of cement were used in sometimes futile efforts to establish a good surface seat. During the cement setting period, flow can resume.

Drilling with fluid weighted to contain potential influx is one solution to this problem. As returns are still directed to the seafloor while drilling continues, it is has been termed ''pump and dump.'' Admittedly this is an expensive approach, and only undertaken in an expensive drilling environment. Brine of viscosified fluid weighted sufficiently to contain the shallow formation pressures is continuously pumped downhole. The unconsolidated, slightly overpressured formations are rapidly penetrated and a gauge or close-to-gauge hole obtained. Casing is run and with no formation fluid influx routinely cemented.

Because huge volumes are needed, frequently the fluid or brine is premixed at shore-based facilities and transported in bulk to the dril site. When mixed at rig site, ''big bags'' of barite or salts (usually calcium chloride) are commonly used to facilitate the rapid mixing necessary to continuously fill the large diameter hole being rapidly generated.

Drilling Program

What is the expected total depth?

Where are the casing points?

Are there other drilling parameters (hole size, bit type, ROP)?

What type of drilling fluid will be used?

What is the low-gravity-solids tolerance level?

What flow rate is planned?

What is the annular velocity in all sections of the borehole?

What is the hole cleaning capability?

What nozzle selection optimization will ensure immediate cuttings

removal from the bottom of the hole?

What are other desired drilling fluid properties (mud weight, plastic

viscosity, yield point, electrical stability)?

Except above listed issues there are still equipment capability, rig design and availability, logistics, the environment issues, and the economics.