Proposal Conventional means of primary cement placement pump the cementing fluids down the casing and well returns are taken from the annulus. This is the most common way of cement placement for the industry and has been used for more than 80 years. Much less commonly used by the industry, but recently gaining in use is the Reverse Circulation of Cement (RCC) technique. When using the RCC technique, the cementing fluids are pumped into the annulus of the well and returns are taken through the casing. The recent acceptance of the RCC technique is mainly driven by economics and state-of-the-art technology bringing an alternative technique. Benefits of the RCC technique can include lowering bottom-hole placement pressure, reducing cement retarder concentration, lowering the time for cement placement, and increasing location safety. The main drawback to the technique is determining when uncontaminated cement is at and around the casing shoe. This paper discusses the benefits and shortcomings of the RCC technique in relation to fluid friction, cement slurry design, location safety, and zonal isolation. The paper illustrates, through a case history, how RCC technique's strengths are obtained while shortcomings are minimized. Field data from a recent job using the RCC technique on a 3100-m gas well in Alberta, Canada, as well as lessons learned from the job, are presented. Introduction One of the common concerns in the industry when it comes to cementing is the potential for lost circulation. While a few different approaches can be taken to address this problem, a viable alternative in reducing equivalent circulating density (ECD) is reverse cementing.1 RCC is a process in which spacer(s) and cement slurries are pumped down the annulus and returns are taken through to the surface casing string (Fig. 1). Cement slurry's location can be determined by two common methods:Utilizing a logging tool and radioactive tracersFluid markers Fluid markers have been the favorite system because no environmental issues are involved and it is more economical. Logging tools and radioactive tracers are more attractive when top of cement (TOC) inside the casing needs to be limited; i.e., when foamed cement systems are used in conjunction with RCC. However, not every well is a prime candidate for RCC. Certain conditions should be present to indicate the necessity of this method. RCC is not an entirely trouble free system. Some disadvantages exist in this system just like any other system that is in use. In the remainder of this paper, the advantages and disadvantages of RCC are discussed in detail. Also, a process is examined to aid with the decision-making when an operator is evaluating the options available to cement a string of casing. Evaluation The following sections detail important advantages, disadvantages, and challenges of using the RCC method. Advantages of RCC RCC can provide the following advantages in wells meeting the requirements for the method:Reduced EDCsImproved mud displacementShorter slurry thickening timesImproved compressive strength developmentImproved safety and environmental managementEasier cement slurry selectionImproved formation production due to less risk of cement invasion into the producing zone

Drilling operations daily generate large amounts of data but surprisingly, a significant proportion of these data are not utilized in a manner that shortens the learning curve and promotes drilling efficiency. The authors, through this paper, demonstrate how drilling analysis methodology helped identify performance gaps in a West Central Canadian field. The above is captured under the much espoused philosophy characterized by the questions:Where are we now?What is possible?How do we get there? By applying this tool, significant cost savings to the tune of CAD$7.3 mln have been achieved as at the time of preparing this paper. Introduction There have been various approaches developed over the years to optimize the well construction process but only a few of these have addressed the subject of improving drilling performance through a systematic analysis of historical data. The drilling analysis concepts described in a companion paper1 were applied to an already optimized field and additional cost savings of 15% were realized as at the time of preparing this document. The driver to the adoption of drilling analysis as a core requirement was prompted by the requirement to reduce drilling cost as a way of improving project economics in the matured sedimentary basins of Western Canada. At the commencement of drilling analysis in the Wild River Field, a total of 41 gas wells have been drilled by Anadarko and its predecessors since the first well was spudded in 1999. Thirteen of these wells were drilled to between 5 and 20 degrees deviation while the rest were drilled as vertical wells with maximum allowable deviation of 2 degrees. Hole sizes and casing schemes were largely similar (Fig 1). The surface holes were drilled with 311 mm bits to about 430 m while the production holes were drilled through the reservoir (Cadomin) to TD in the Fernie formation at 3050 m. The wells, from spud to rig release, were initially drilled between 56 and 70 days at the onset of field development, but with more wells drilled, drilling operations time improved and flattened at between 22 and 38 days, averaging 29 days for well depths of approximately 3050 m (Fig 2). The well cost associated with the drilling of these wells also improved from CAD$2.50 - CAD$3.75 mln (in money of the day terms) at the beginning of field development to an average of CAD$1.76 mln (or $570/m) before performing drilling analysis. The public domain data from 40 other wells drilled by 4 other operators in the Wild River field were also studied and the drilling time results showed similar performance level as Anadarko's (i.e spud to rig release time of 30 days, Fig A-1).

fax 01-972-952-9435. ProposalConventional means of primary cement placement pump the cementing fluids down the casing and well returns are taken from the annulus. This is the most common way of cement placement for the industry and has been used for more than 80 years. Much less commonly used by the industry, but recently gaining in use is the Reverse Circulation of Cement (RCC) technique. When using the RCC technique, the cementing fluids are pumped into the annulus of the well and returns are taken through the casing.The recent acceptance of the RCC technique is mainly driven by economics and state-of-the-art technology bringing an alternative technique. Benefits of the RCC technique can include lowering bottom-hole placement pressure, reducing cement retarder concentration, lowering the time for cement placement, and increasing location safety. The main drawback to the technique is determining when uncontaminated cement is at and around the casing shoe.This paper discusses the benefits and shortcomings of the RCC technique in relation to fluid friction, cement slurry design, location safety, and zonal isolation. The paper illustrates, through a case history, how RCC technique's strengths are obtained while shortcomings are minimized. Field data from a recent job using the RCC technique on a 3100-m gas well in Alberta, Canada, as well as lessons learned from the job, are presented.