Casing wear is often a problem in deep wells where doglegs and large tension loads on the drill string combine to produce high lateral loads where the drill string contacts the casing. Casing wear can result in blowouts, lost production, and other hazardous and expensive problems. A mathematical model which describes casing wear in terms of hole geometry, casing/tool-joint material, mud system, and drilling program, has been developed and verified. Over 300 laboratory wear tests have provided wear factors which allow the model to be applied to a wide range of drilling situations. The model has been incorporated into a computer program, CWEAR. The prediction of dogleg severity and casing wear is seriously compromised by directional surveys in which the station spacing is 100 ft or greater. Through the laboratory test program, means to reduce casing wear rate have been demonstrated and applied in the field. Mud lubricants, tool-joint materials, pipe protectors, and casing materials and internal coatings have all been examined as possible means to reduce casing wear. Some mud lubricants significantly reduce frictional drag; others do not. Because a mud lubricant significantly reduces frictional drag does not imply that it will also reduce the casing wear rate. Newer, proprietary tool-joint coating materials have proven effective in reducing casing wear, while continuing to protect the tool joints in open hole. Pipe protectors have proven to be one of the better means of reducing casing wear. Laboratory experiments have demonstrated severe operational difficulties of these protectors. Several of the protector manufacturers are now engaged in development programs to improve their products. Inadequacies in the available methods of measuring casing wear in the field have been demonstrated. As a result of this work, at least two new casing wear measurement tools are under development. GOALS OF THE PROJECT The goals of our casing wear technology project are to:Predict Casing WearMeasure Casing WearReduce Casing WearPredict Burst and Collapse of Worn Casing To predict casing wear requires a mathematical description of the casing wear process. To implement this model requires experimental determination of the wear factors which are an integral part of the casing wear model. Such a model has been developed and verified. The model has been incorporated into a computer program, CWEAR, which has been used as both a planning and operational tool. More than 300 laboratory tests have been performed to determine wear factors which allow the model to be applied to a wide range of well geometries and drilling programs. Measurement of casing wear in the field has proven to be poor at best. Experimental evaluation of casing wear logging tools showed the need for improvement.

Drilled wellbores have evolved from nearly vertical, shallow holes to tortuous, deep, directionally drilled wells. As wellbore geometries have increased in complexity, so has the potential of damage resulting from casing wear. It is not unusual to routinely install ditch magnets in the returned drilling fluid circuit to catch the iron filings created by tool joint wear against the casing or riser interior wall. While most "straight" holes attempt to control inclination, azimuth control is often times neglected, potentially creating a tortuous path. In directionally drilled holes, including horizontal and multi-lateral wells, the drill string tension holds the rotating tool joints against the inner wall of the casing for extended periods. This results in the generation of crescent shaped wear grooves (key seating) in the inner wall of the casing, often dangerously weakening casing or riser strings making them more susceptible to burst or collapse. Some investigators have sought to quantify this damage process. Computer models describe, measure, and predict damage from casing or riser wear. From these on-going studies, advances in technology continue to minimize casing and riser wear. More than 475 8-hour casing and riser wear tests have been conducted, producing the largest casing/riser wear database known. Analysis of this database led to the development of the contact pressure threshold concept, consistently demonstrating its validity. When a rotating tool joint impinges against the inner wall of a casing or riser, a crescent shaped groove is worn into the inner wall. The volume worn away from the casing or riser wall is proportional to the frictional work done on the inner wall by the tool joint. This is mathematically presented in the equation: Equation (1) Experimentally determined over an 8-hour testing period, the Casing Wear Factor, WF, is then defined as the ratio of friction factor to specific energy, as shown in equation 2, Equation (2) and the sliding distance is defined as shown in equation 3, Equation (3) If the length of a joint of drill pipe is Ldp, and the length of a tool joint is Ltj, then Equation (4) As an example: If Ldp = 30 ft., and Ltj = 14 inches, f = 0.039. Thus, the volume of casing wall removed per foot in time t hours is given by equation 5. Equation (5) To establish a benchmark test for comparison of casing wear factors, a set of standard dimensions and conditions for conducting the wear testing was established. These dimensions and conditions are shown in Table 1. Since discussions of the testing program and the significance of the measured wear characteristics are presented in other publications, they will not be repeated here.

SU~~~a DrNIi~gj Riser Wear: A Case Historỹ .?.PO=, Ph~!!@ P@~OIQUrn CO,:ndFLW. I-lall Jr., Maurer Engineering, lfIC. SPE Members -~1*. WWIAOC DrilllrKIConference. This peper wee prepemdfor preeentetionat the 1S'96SPE/lADC DrillingCaWerenoeheld in AmeIefdam,28 Februery-2 Merch 1SS5 mie pper weeeekuedforpresentationby an SPE/lADCPmgrem(%mmlneetoibwingreviewof Information wnteined in an abetreotwbmined =~. *not been revkwed by theIntwmuonel AwoobtbncdOrllMng by the euthor(a). Contenteof the peper, meterlel,ee preeented,doee not Catrdomof the Sodetyof PetroleumEn@wereenduee ubJeottooorreotk+I bythewthc@). The newwerily refteoteny poeitiond the SPE or IADC, their ofHoere, or membere.Pepere prewnted et SPHINX meetingeere wbjeotto publiwtbn revk#by EditorlelCommSteeeofthe SPEend 1~.Pm~mqk~toen~dtititW~~e. Illuetmtbnemeynotbecepied.l%e abstmotehauld oonteinoonepbuwe dmowleqrnent d whereend bywhomthe peperie prwnntd WriteLilwuien, SPE, P.O. SoxS22SS6,Rkhenleon, TX7SOSNSSE, U.S.A. Telex, 162246 SPEUT. ABSTRACTWeer in subsea drilling risers and BOP equipmant while drilling can be an expansive problem. If the wear causes loss of riser integrity the risk to personnel and equipment is potentially significant due to the well control situation that could result. This papar presents information on a serious riser/BOP wear occurrence that resulted in serious well control problems and an expensive equipment repair. The case study presented here occurred in only 295 ft of water in a relatively short period of drilling time. The approximate cost of the resulting problems was in excess of US$3.5 million. This papar will also present a simpie model that can be used to estimate the wear in a riser and flax joint. The calculations in this paper will provide a means to detem"na the relative effects of such parameters as riser angle and tooljoint hardbanding abrasiveness. WRh this knowledge it is possible to develop an informed riser wear management program.

Concrete condition assessing penetrometers need to be able to distinguish between making contact with a hard (concrete) surface as opposed to a semi-solid (corroded concrete) surface. If a hard surface is mistaken for a soft surface, concrete corrosion may be over-estimated, with the potential for triggering unnecessary remediation works. Unfortunately, the variably-angled surface of a concrete pipe can cause the tip of a force-sensing tactile penetrometer to slip and thus to make this mistake. We investigated whether different shaped tips of a cylindrical penetrometer were better than others at maintaining contact with concrete and not slipping. We designed a range of simple symmetric tip shapes, controlled by a single superellipse parameter. We performed a finite element analysis of these parametric models in SolidWorks before machining in stainless steel. We tested our penetrometer tips on a concrete paver cut to four angles at 20∘ increments. The results indicate that penetrometers with a squircle-shaped steel tip (a=b=1,n=4) have the least slip, in the context of concrete condition assessment.