SPE Members Abstract The adverse effects of inadequate fluid-loss control associated with gravel-packed completions is well known. Controlling fluid losses to the formation before and after pack placement is critical to ultimately achieving optimum productivity from a given well for the following two reasons:–Fluid-loss control is necessary to prevent losses of expensive high-density brines, sometimes used for well control in high-permeability, unconsolidated formations. The costly loss of expensive brines can also lead to critically unsafe well conditions, where high overbalance pressures are required to control highly geopressured zones.–Dense brines have been reported as being difficult to unload from formations once losses have occurred. Calcium and zinc-bromide brines can form highly stable, acid-insoluble compounds when reacted with some formation brines. Because of the high density of these brines, stratification tends to further inhibit their removal. The most effective means of preventing the formation damage described is to limit completion brine losses to the formation. Introduction A variety of fluid-loss control materials have been used and evaluated, including foams, oil-soluble resins, acid-soluble particulates, graded salt slurries, linear viscoelastic polymers, and heavy metal-crosslinked polymers. Their comparative effectiveness is well documented. Most attain their fluid-loss control from the presence of solvent-specific solids, or from hydrated linear polymers that rely on filter-cake buildup and on viscoelasticity to inhibit flow into and through the formation. Oil-soluble resins generally clean up well when they are thoroughly contacted with solvent. Tests have shown, however, that such resin, lodged in perforation tunnels, may remain isolated from solvent for extremely long periods, thus restricting well production. Recent testing has shown that particulate systems, i.e., graded salt slurries, particularly those using polymers and gums for particle suspension, can be quite damaging to formations and difficult to remove from perforation tunnels. Himes et al. reported less than 10% regained permeability after treatments into a Berea core with a salt system containing graded salt in a xanthan gum base in a 10% NaCl solution. P. 743

Decades after the first completion in the Gulf of Mexico (GOM) continental shelf, the logical expansion of these mature assets has extended into reservoirs that are deeper, hotter, and higher-pressured than previously completed wells. The industry refers to wells in this category as highpressure/ high-temperature (HPHT) and these types of wells can cause extreme completion challenges. HPHT formations also tend to have low permeabilities, which is the opposite of most GOM reservoirs. To make these low-permeability formations economical in an offshore environment, it is imperative that stimulation treatments be completely effective. Contrary to conventional GOM shelf completions, this well did not require the use of any sand face completion equipment because the formation is well consolidated. Due to the lack of screens, the engineers deemed it necessary to perform a hydraulic-fracturing treatment using a proppant coated with a surface modifying agent that inhibits flowback of proppant to the production facilities. This type of effective completion was instrumental in making the project economically successful and allowed the well to achieve post-hydraulic fracture production rates up to 35 MMscf/D. No further type of stimulation has been necessary and the well has continued to perform at a level above that of production rates before the fracturing treatment. Introduction The West Cameron 62 (WC 62) field, located on the continental shelf just south of Louisiana at a water depth of 35 feet, saw its first well completed over 20 years ago. Since that time, more than 30 different intervals have been completed at depths ranging from a few thousand feet to over ten thousand feet. In recent years, it has become necessary to focus on reservoirs that exist in the 18,000-20,000 ft true vertical depth (TVD) range. At these depths, the pressures and temperatures of the formation trend toward the extreme of what current technology allows when completion equipment and fluids are considered. The WC 62 A-2 well was completed at these depths in the Cris R formation. As shown in Fig. 1, the Cris R sand is located between 17,843- and 18,021-ft TVD, which correlates to 19,789- and 19,976-ft measured depth (MD). Table 1 shows the perforated intervals selected to target the cleaner, higher-resistivity zones and to help ensure against the production of fines from the shale intervals. The initial bottomhole pressure (BHP) for the Cris R formation was measured at 16,500 psi at mid-perf. The bottomhole temperature (BHT) at mid-perf was 356°F. Table 1-Perforation Intervals (available in full paper) Also contrary to conventional GOM reservoirs, which typically have average permeabilities in excess of 50 md, the permeability of the Cris R sand averaged only 0.64 md. The porosity of 18% was also significantly lower than the wellsorted formations found at shallower depths. In fact, along with permeability and porosity, the rock mechanics fall more in line with typical south Texas "hard rock" reservoirs such as the Wilcox and Frio formations. The rock mechanics, as detailed in Table 2, show Young's modulus in excess of 2.50E6 psi in the sand and 2.20E6 in the shale boundary layers. Table 2-Rock Mechanics for Cris R Sand (available in full paper)

Numerous additives and fluid systems have been introduced to the oil industry for the control of fluid loss or to provide a norunechanical means to isolate intervals. Most are either viscosified fluids and/or solid particulates.There are advantages and disadvantages to both types. Recent testing has shown many systems to be quite damaging to the intervals they are to protect, especially in control of high differential pressures.Research perfonned over the last few years has led to the development of a novel fluid loss control agent that is capable of conb'olling fluid loss without imposing severe penneability damage on a potential producing formation. Laboratory tests have shown the material to be much less damaging than particulate systems, such as graded salt slurries, and capable of holding higber differential pressures than simple gelled brines.Regained penneahility values have been as high as 100%.Typical regain permeability values are around 90% compared to much less for other systems tested. The fluid system can be prepared from most brine solutions and weight adjusted to match densities of fluids in the wellbore.

atrial synchronous ventricular pacing (VDD) and ventricular sensing and pacing (VVI) modes and elucidate its relationship with clinical, hemodynamic and electrophysiological variables.Among 35 patients followed up in our pacemaker clinic with pacemakers implanted for CAVB 25 patients were assigned to VDD mode group and 10 patients to VVI mode group. Control group consists of 20 age and gendermatched patients with coronary artery disease and normal AV conduction. Patients of VDD pacing group did not differ by means of HRV from the Control group of patients, while patients of VVI group had significantly higher (p<0.05) values of indices of sympathetic modulation (LFNU) and sympathovagal balance (LF/HF) ratio as compared with Control and VDD groups. Multiple regression analysis demonstrated that HRV indices did not correlate with age, EF, time from implantation of pacemaker but were significantly related with cardiac output and mean PR interval in patients with VDD mode of pacing.Thus, atrial synchronous ventricular pacing normalizes autonomic control of heart rate in patients with CAVB being the same as in patients with normal AV conduction, possibly through preservation of the atrioventricular electrical and hemodynamic sequences, while VVI mode is characterized by higher response of the sinus node to sympathetic modulation. The predictive value of the latter finding needs elucidation. P.2.9 VENTRICULAR PACING THRESHOLDS FOLLOWING HIGH-ENERGY VENTRICULAR DEFIBRILLATION SHOCKS Y. Yamanouchi, H. Urata. Fukuoka University Chikushi Hospital, JapanIncreased ventricular pacing thresholds have been observed following monophasic waveform shocks in implantable cardioverter defibrillators (icds). This study aimed to examine such changes following high-energy biphasic shocks in icds.Method: Ten episodes of VF were induced every 10 minutes in 10 pigs (23.1±3.0 kg). After 10 seconds of VF a 40J biphasic shock (total 10 shocks) was delivered for successful defibrillation in the true-bipolar sensing lead system of the ICD. Ventricular bipolar pacing thresholds before and after these shocks were evaluated at one-minute intervals.Results: The mean pacing threshold before shock delivered was 0.066 ± 0.059 uj. Those of the first, second and third minutes after the first shock were 0.052 ± 0.061 uj、0.044 ± 0.039 uj, respectively; showing that pacing thresholds gradually decreased.