Friction? Let it slide

Tim Wagner, ProOne, USA, introduces a new lubricant that addresses the major drilling challenge, friction, amongst other characteristics.

Horizontal and vertical drilling operations both face the same major drilling challenge: friction. Successful lubricant use can solve this problem, along with aiding the downhole operation. Operators seek out the solution to costly problems such as freeing stuck pipe or finishing a well without hole collapse, with a new lubricant product promising significant cost savings by eliminating excessive trips, and saving drill bits and mud motors.

Six years since its introduction, ProOne’s XPL+, is sold in large quantities through 250 US locations, 60 in Canada and 38 internationally exclusively by the recent NOV spin-off, DistributionNOW (DNOW). XPL+ stands for Xtreme Pressure Lubricant after being code-named ProOne Downhole Drilling Fluid Treatment (PODHDT) during R&D.

Southern California case study

A recent case study illustrates the impact ProOne XPL+ technology had on reducing torque and drag. When results were in at a drilling site in southern California, west/northwest of Bakersfield, a spokesman concluded, “ProOne solved our torque and drag problem immediately and significantly in this highly deviated well.”

The basis of this comment began with drilling of a deep, highly deviated well with a 12.8 ppg clay-based mud system. During drilling of a 6 ? in. hole below 12 500 ft (well deviation greater than 87 in.), torque and drag levels were both high and erratic. With a projected 13 000 ft total depth (TD), rig top drive capacity was rated at 9500 ft-lbs with existing drill pipe. Oil as a lubricant was ruled out for two reasons: to not interfere with downhole imaging and to not negatively affect the mud log.

Prior to bringing in ProOne as a mud additive, the objective of drilling several hundred feet extra to 13 500 ft became problematic after attempting to drill below 12 500 ft in the extremely directional well. Therefore, facing the greater TD objective, and additionally dealing with hole configuration, torque and drag, the operator decided on XPL+ as the new additive. By building the PODHDT up to 3% by volume to specifically reduce the high torque, it was additionally determined that ProOne might be helpful with the mud log and imaging tool.

Calculation of the main circulation mud pit indicated that the additive supplier should deliver twenty-four product drums because that would provide a volume concentration of 3% in the rig’s active mud system. For four consecutive hours rig personnel added XPL+ in 100 bbls, 5% by volume pills/sweeps to achieve the 3% concentration. As addition of the product continued, so did the drilling. Subsequently, well completion moved ahead without a hitch and significantly without torque or drag problems.

Results were notable, including a torque reduction from 8500 ft-lbs to 6000 ft-lbs or almost 30%. The company reduced drag by 40% from 84 000 lbs to 50 000 lbs and circulating drag by 60% from 30 000 lbs to 12 000 lbs. Other figures which stood out included (a) a 15% improvement in rate of penetration (ROP), from 135 ft/h to 148 - 155 ft/h (b) torque circulating off bottom before ProOne was added, then 6600 ft-lbs and down to 5200 ft-lbs after the additive’s addition. Neither imaging nor mud log were affected.

Additionally, because of the lubricity provided by XPL+, the well’s rig capacity was extended and readings on torque and drag ceased being erratic. The latter meant that during drilling there was more consistent weight on bit (WOB) as one of the various secondary enhancements to the drilling.

From R&D to the field

The technological secret to XPL+ is as much common sense as science, in the way its development is based on ‘connecting the dots’ to combat friction. In the product’s name, the plus sign represents how the positively charged molecular structure reverses polarisation of the base lubricants’ molecular structure. By reducing the static electromagnetic field with a positive charge, electrolysis is reduced.

Onsite, mixing the slurry at a 3 - 5% concentrate rate, the rheology is completely surrounded with lubrication for optimum performance. Aside from delivering new savings in time, costs and equipment wear, when this lubricant bonds to metal it creates a unique surface layer. In terms of the mixing itself, XPL+ emulsifies in all water-based muds, oil-based muds and brines, and effectively remains emulsified better than other lubricants utilised in downhole drilling.

While protecting metal under extreme downhole conditions, it also seals out unwanted intrusions such as hardened layers, water and salts. Also, by generating a layer on all metal surfaces, corrosion is virtually 100% blocked off and the cost-effective mix ratios reduce friction more than ever possible before. Temperatures are an ongoing theme in the XPL+ field performance, where the additive has functioned effectively up to 340°C.

Determined to hold the additive to the highest standards, ProOne had it tested by internationally respected industry labs. Lubricity coefficient testing showed an 82% decrease from 0.35 to 0.062 at 78°F and a 93% decrease from 0.34 to 0.024 at 200°F.

Wide-ranging attributes

The same technology that separates ProOne’s mud additive from other downhole lubricants on the market also delivers a wide variety of benefits aside from torque/drag reduction and increased ROP for operators. Additional performance benefits that were solved include doglegs, long horizontals, spiralled holes, top drive overheating, low ROP, chopped holes, short drill bit life, stuck pipe, wearing out mud motors and excessive trips.

For example, with ROP performance being a consistent challenge, the primary capability of the ProOne lubricant is that it reduces friction system-wide in downhole drilling. That reduces torque, as noted, and consequently increases the ROP; sometimes the increase is as high as 50% in the curve. Meanwhile, as drilling continues, heat exposure along with inevitable wear on the drill bit can drive up costs by the tens of thousands of dollars in bits which normally have to be replaced. In contrast, this additive’s lubricity results in bits being replaced less often and typically saving more than one bit in each well drilled (with bits costing into the six figures each from time to time).

Of course, possibly the drilling aspect drawing the most attention from a time/cost perspective is reducing how many trips are required on a per well basis. By most generally accepted estimates, savings by operators using the ProOne additive for system-wide lubrication have tallied between US$100 000 - 500 000 on a representative well depth. That level of savings also applies to achieving higher ROP and reducing disposal costs.

By increasing the lubricity more than fifty times versus conventional lubricants, operators have quickly discovered more spin-off effects. These include top load equipment having to endure much less stress and energy, thus becoming a considerably more efficient operating system, less time required for inserting casing and substantially fewer downhole string and tool failures.

Of those who have utilised this lubricant on hundreds of wells throughout North America, many operators have also experienced its value in other ways, such as straighter verticals with less corkscrewing, drilling the curve in half the time, plus sliding the liner, setting casing quicker and markedly reducing hook load, to name but a few.

Based on the actuality that a well of average depth, or 15 000 ft, may require as many as four drill mud motors, any technological advance that can reduce going through that many motors is welcome to operators, from small independents to majors. For example, motor degradation has previously seemed unavoidable since seals fail due to heat, chemicals and vibration. Now, because ProOne’s lubricant overcomes those specific factors, fewer drill motors are necessary, while the aforementioned excessive trips and drill string repairs are greatly minimised.

Since its introduction to the oilfield in 2008, XPL+ has become field-proven on a widespread basis simply because more and more operators are successfully using it. Of other examples, one is a New Mexico case study on the longest lateral in state history (19 770 ft TD).

According to the company, laying as much 5in. string as they did for 12 000 ft of lateral should have taken twice the hook load in that formation. Instead, the operator experienced a 50% drop in torque (maxed out from 30 000 - 15 000 ft-lbs) and a 28% ROP increase. In additional direct results, there was decreased drag on trip out and 25 000 WOB.

In another case study from a major operator in Laredo, Texas, drill pipe had become stuck at an 11 400 ft depth. According to the company, they had tried ‘the leading spotting fluid,’ but it proved ineffective in achieving the recovery. After agreeing to ‘give it a try’ with ProOne’s lubricant, the string was successfully extracted from the hole after four sweeps.

Biodegradable solution

With the environment an increasingly important issue, ProOne took extra steps to ensure that its downhole drilling fluid is earth-friendly. As a result, it is biodegradable in line with very strict global standards and in terms of the world’s oceans, which constitute most of the planet, it is non-toxic to marine life.

Test results speak for themselves, including first and foremost the OECD Biodegradation Test. In this stringent test, 60% degradation was reached within 16 days and with a 83% degradation plateau within 31 days demonstrating ultimate biodegradation. In addition, the 96 hr Fathead Minnow Test was passed, as were the Mysidopsis Bahia 96 hr LC50 at 3% and Mysidopsis Bahia 96 hr LC50 at 5%.

None of these unique lubricant capabilities and comprehensive results have come as a surprise to engineers at ProOne, headquartered jointly in Houston, Texas and Orange County, California (USA), because they knew they ‘were onto something’ when bench cross axis friction machine test results were recorded. The bearing, which showed severe damage at only 4000 psi with regular lubricants showed only minimal damage at 200 000 psi (50 x more) with XPL+ – and operators worldwide are the direct beneficiaries through unprecedented time and cost savings.

Adapted for by David Bizley

Published on 19/02/2015

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