In palliative patients, depressive symptoms should not be judged as a normal attendant of the terminal illness situation. Instead, patients should be referred to appropriate support services for pharmacological or psychological treatment. Spousal caregivers and caregivers who are socially not well integrated are in particular need of support. Attention to the financial burden of family caregivers is also very important. Due to the existing correlation between the psychological situation of palliative patients and their caring relatives, couples must be considered an emotional system rather than just two individuals.

We examined psychological parameters in family caregivers of palliative cancer patients before and after the death of the patients. Caregivers' data about depression and anxiety (Hospital Anxiety and Depression Scale), quality-of-life (Short Form-8 Health Survey), and social support (Oslo Social Support Scale) were collected at the beginning of home care (t1) and 2 months after the patient had died (t2). Regression models were employed to examine factors related to depression and anxiety in the bereaved caregivers. We interviewed 72 relatives, who were the primary caregiver of a patient. One-third (31.9%) of caregivers had high anxiety levels and 29.2% had high depression levels (t1, cut-off = 10). At t2, anxiety and depression had decreased significantly. There were no changes in quality-of-life over time. At both points of assessments, quality-of-life was lower than in the general population. Relevant factors for higher anxiety and depression in the bereaved caregivers were high levels of distress at t1, insufficient social support and low physical function. Bereaved caregivers were particularly depressed when they had been the spouse of the patient. Healthcare professionals should consider social isolation of caring relatives both during homecare and afterwards. Thus, it seems to be important to routinely offer support to spouses.

Summary Two new polyacrylamide processes for water control in producing wells improve the efficiency of conventional polyacrylamide treatment withoutinducing any risk of well plugging by crosslinkers. Treatment plugging bycrosslinkers. Treatment of a gas-storage well strongly decreased waterproduction without any adverse effect on gas injection or production for atleast 3 years. Introduction Excessive water production is frequently encountered during the lifetime ofoil- or gas-producing wells. It is generally responsible for both a rapidproductivity decline and an increase in operating costs caused by the handlingand treating of large amounts of water. It may also induce some secondaryproblems, such as fines or sand migration problems, such as fines or sandmigration in the near-wellbore portion of the reservoir, that also contributeto the deterioration of well productivity. The result often is a prematureshut-in of the well because premature shut-in of the well because productionhas become uneconomical. production has become uneconomical. Direct treatmentsof producing wells to reduce water production may be classified in two maincategories, each one better suited to specific conditions. If water andhydrocarbon zones are clearly separated, processes using permanent barriers, which can be selectively placed in the water zone, generally give good results. This impermeable barrier, which aims to stop the flow of all fluids, may beformed by cements, resins, or silicate gels. On the other hand, when oil or gasand water zones are not easily distinguishable, the use of permanent plugsbecomes very risky. It is generally preferable to place a selective barrier inthe whole pay zone, which blocks water but remains permeable to oil or gas. Inthis case, the systems used are based on hydrosoluble polymers. It has been shown that, after injection of high-molecular-weighthydrosoluble polymers in the near-wellbore region of a polymers in thenear-wellbore region of a reservoir, the polymer adsorbed on the rock has theproperty to restrain water flow with little effect on oil or gas flow. Moreover, polymer adsorption appears to be almost polymer adsorption appears tobe almost irreversible, thus making the process efficient for long periods oftime. The polymers most widely used in this process are polyacrylamides havinga certain percentage polyacrylamides having a certain percentage (generallyless than 30%) of acrylate functions. These polymers, readily available aspowders or emulsions, are relatively cheap. powders or emulsions, arerelatively cheap. They have a high viscosifying power, especially in softwater, and give high values of permeability reduction to brine when they areabsorbed on reservoir rocks. Conventional processes are based on the adsorption properties of singlehigh-molecuiar-weight polyacrylamides. Adsorbed polymolecules form an almostimpenetrable polymolecules form an almost impenetrable layer on pore walls, thereby effectively restraining the flow of water (the wetting phase) while thecenter of the pore channels phase) while the center of the pore channelsremains free for the flow of hydrocarbons (the nonwetting phase) Fig. 1a is aschematic of this process. The efficiency of the process is directly related tothe thickness of the process is directly related to the thickness of theadsorbed layer compared to pore size. In high-permeability or fissuredreservoirs, the channels through which water flows are an order of magnitudelarger than the macromolecular size, rendering the process quite inefficient. To treat such cases, several processes using crosslinking agents have beenprocesses using crosslinking agents have been developed. Crosslinkers aregenerally multivalent metal ions, which can build polymer networks in the porechannels (Fig. 1b). Although such treatments provide a greater ability to blockwater, they also carry the risk of losing some selectivity, indeed, because thecenter of the pore channels is occupied by the polymer network, the flow of thenonwetting hydrocarbon phase becomes restrained in the same way as that ofwater. Two new polyacrylamide-based treatments improve the efficiency ofconventional processes without the risk of well impairments associated withcrosslinked systems. Both are based on the in-situ swelling of the adsorbedpolymer layer. Process A is very efficient for treating reservoirs havinglow-salinity brines; Process B covers a greater range of salinity. Both processes have been evaluated in the laboratory through two-phase flowtests in sand and sandstone cores. We could thus determine the changes in waterand oil or gas relative permeabilities induced by the treatments. The swellingof the adsorbed polymer layer was followed by the measurement polymer layer wasfollowed by the measurement of permeability reductions to brine before andafter treatment. Process A was applied to a gas-storage well in June 1986. See the Cerviile-Velaine Field Test section for results of this test. Process Description Process Description Process A. Process A uses theproperties Process A. Process A uses the properties of the acrylamide/acrylatecopolymer's (HPAM) coiled molecule that cause it to shrink in the presence ofsalts and to swell in soft water (Fig. 2). JPT P. 862

SPE Members Abstract Polyacrylamide and polysaccharide adsorption on natural water-wet sand and sandstones is shown to modify markedly the flow behavior of both water and oil. At residual oil saturation, the quantity of adsorbed polymer per gram of rock is found to be almost the same as at full water saturation, but the permeability reduction to water is increased by the presence of trapped oil droplets which reduce the flow cross-section for the water phase. The presence of adsorbed polymer always induces an increase in the water irreducible saturation due to polymer hydration water which is not expelled by contact with oil. However the oil relative permeability is shown to be little affected by adsorbed polymer over the remaining saturation range. On the basis of a polymer over the remaining saturation range. On the basis of a capillary two-phase flow model, this phenomenon is interpreted as the result of the competition between the reduction of flow cross-sections and the enhancement of the water-wettability of the rock, with both effects having the same origin, i.e. the polymer adsorption process. polymer adsorption process Introduction High-molecular-weight water-soluble polymers are widely used as thickening agents in the oilfield industry. They can be injected into the near-wellbore zone of a reservoir as in well treatments, or deeper into the formation as in chemical flooding where polymer slugs provide the mobility control of the injected fluids. During the propagation of a polymer slug through a reservoir, a fraction of the polymer is permanently fixed on the rock by a process called "adsorption." The polymer adsorption process has two characteristics which make it different from adsorption of other chemicals:it is practically irreversible;it leaves on the surface of the rock an adsorbed polymer layer whose thickness is of the same order of magnitude as pore size. Both characteristics seem to be closely related to the high molecular weight of this class of products. Since each macromolecule is constituted of several products. Since each macromolecule is constituted of several thousands of subunits, the linkage of only some of them on the surface of the solid fixes the whole macromolecule. Moreover, the free subunits favor the formations of loops and tails which give the adsorbed polymer molecules a size comparable to free ones. Even if the bonding force between a polymer subunit and an adsorption site of the rock is weak, the sum of several bonding forces generally results in a strong attachment of the polymer molecule to this rock. This phenomenon explains why polymer molecule to this rock. This phenomenon explains why nonionic or weakly anionic polymers adsorb on solids whose average surface charge is negative. Electrostatic repulsions between polymer molecules and pore walls are not sufficient in this case to destroy all the bonding forces which tend to fix the polymer to the solid. polymer to the solid. A recent study has shown that, by a slow process, there is a permanent exchange between adsorbed and free polymer molecules in the surrounding solution. However, as soon as free molecules are removed by waterflooding, this process stops and adsorbed molecules appear to be permanently fixed on the solid. This phenomenon explains why, both in laboratory core flow experiments and in field cases, we observe that the portions of the reservoir which have "seen" polymer remain affected over long periods of time by the presence of adsorbed polymer, even after the washing out of this zone. As reported before, the hydrodynamic size of these high-molecular-weight polymers in solution is in the range of a um. The average pore size of most reservoir rocks is also of the same order of magnitude, ranging between a fraction of a um in the tighest formations to more than 10 um in the more permeable ones. It is thus expected that the presence of an permeable ones. It is thus expected that the presence of an adsorbed polymer layer at the pore wall will have, in most cases, a marked incidence on the flow of fluids through the pore channels. The effect of adsorbed polymer on water flow has been intensively studied in the past within the framework of polymer flooding studies. Adsorption of polymer in a core is generally found to decrease its permeability to water. This effect is characterized by a number called "permeability reduction" or "i residual resistance factor," which is equal to the ratio of initial-to-final permeability. P. 297

Low shear injection of different-nature polymers through various sand and sandstone cores has been performed to study the specific influence of adsorption on polymer propagation and flow behavior. As predicted by the deletion layer theory, polymer propagates faster than brine through non adsorbing porous media giving a mobility ratio less than solution viscosity ratio. An increase in clay content both decreases permeability and increases polymer adsorption. Thus a polymer propagates through pores having a smaller cross-section at a lower rate. When pore sizes become close to macromolecule size, polymer adsorbs, forming bridges in pore throats, thus giving very poor and irregular propagation rates. A dynamic method for adsorption measurements on heterogeneous rocks is proposed. Our experimental results effectively fit a capillary flow model with a crossflow section reduced by an impenetrable adsorbed layer. Introduction High-molecular-weight water soluble polymers are used in many oil field applications ranging from drilling to chemical flooding. Their high viscosifying power is primarily due to their large macromolecular size which in turn is often in the same range as pore size. As an example, an usual EOR grade xanthan gum molecule has a rod length of approximately 1 40m and currently is injected 2 into reservoir rocks with permeability k = 0.1 40m and porosity phi = 0.20. By applying the capillary bundle model the average pore throat diameter can be taker. as 2 (8 k/phi) 2.0 40m. If we consider that pore distribution can be pretty large in natural sansdstones, a significant number of pores will thus be smaller than the polymer molecules. Yet, at high shear rates, polymer molecules in solution tend to orientate in the direction of flow and become deformed. This phenomenon, responsible for their shear thinning behavior (see, for example, the rheological curve in Fig.2), allows the macromolecules to pass through pores of smaller size than their own size. Nevertheless. as the shear rate decreases, hydrodynamic forces become weaker and the molecules less orientated in the direction of flow. When polymer molecules are subjected only to Brownian motion, the solutions viscosity finally reach a constant value (Newtonian regime). A xanthan gum molecule then behaves like a sphere 1 40m in diameter (its rod length) and obviously cannot easily pass through pores of smaller size. When a polymer solution is injected into a formation a radial flow takes place. hear rate y is high (several hundred of s) just around the well bore but decreases proportionally to R (R being the invasion radius). At some distance from the well bore, hydrodynamic force become too weak to force the polymer molecules to pass through small pores. Propagation of the polymer thus becomes a problem, at least in low permeability reservoirs. Propagation of polymers is also hindered by the tendency of polymer molecules to adsorb onto the rock. Adsorption of high molecular weight macromolecules is known to be largely irreversible. Significant desorption has been observed only at shear rates exceeding 2000s-1. At low shear rates, although permanent exchanges take place between adsorbed and free polymer molecules, the net quantity of adsorbed polymer does not vary over long periods. P. 327^