No abstract

This paper presents the results of a study into the post-shutdown recovery behaviour of coal seam gas (CSG) wells and its application to estimating long-term field turndown capacity incorporating the impact of well performance recovery postshutdown. Queensland, Australia is currently host to a number of CSG to liquefied natural gas (LNG) projects under development. These projects aim to develop Queensland's vast CSG resources to supply domestic and international gas markets. However, the need to build field deliverability prior to the availability of export gas markets presents a significant challenge. CSG wells must be dewatered while gas production may be constrained. The ability to manage and forecast production performance in field turndown scenario is therefore critical. A study of production data from CSG production interruption events was conducted to determine how wells reacted to turndown of gas production rates. The study considered various production management strategies including partial choking and complete shut in of selected producers. Implications of the work include identification of criteria for selecting wells that are suitable for long-term turndown, the formulation of operational guidelines for minimising adverse post-shutdown production impacts, and estimation of long-term field turndown capacity through the application of the study results to a field production model.

Chronic subacute rumen acidosis is a significant concern in the dairy industry. The syndrome results from a variety of causes including insufficient transition time from dry cow to high production diets, too high a level of fermentable feedstuff in the diet (or conversely too low a level of effective fibre) or inadequate feedbunk management which allows boluses of highly fermentable feed to reach the rumen. Nordlund et al have published a detailed review of the etiology and clinical signs.1 Although the disease generally does not cause overt clinical signs, it can have serious implications on herd health and production. Herd level problems attributed to the syndrome include chronic laminitis, poor appetite or cyclical feed intake, poor body condition in spite of adequate energy intake, hemoptysis, unexplained abscesses, intermittent diarrhea, and high herd cull rates for poorly defined health problems.2 The absence of obvious clinical signs makes diagnosis of subacute rumen acidosis difficult. By the time the animal shows symptoms of the syndrome, several weeks may have passed, making diagnostic tests inconclusive or misleading. As a result, in dairy herds at high risk, because of feeding management practices, a subsample of the herd, consisting of cows in transition and cows at peak production should have their rumen pH monitored.

Cathartics are chemicals that promote defecation. Saline cathartics are salts of poorly absorbed ions for example the cation magesium or the anions sulphate, phosphate, tartrate or citrate. Although these chemicals are not absorbed from the intestine they are osmotically active and attract and retain fluid within the intestinal tract and in this way promote defecation. Saline cathartics that are commonly used in cattle practice include magnesium sulphate (Epsom salts), sodium sulphate (Glauber's salts), magnesium oxide and magnesium hydroxide. These latter two compounds are primarily used as antacids in the treatment of rumen acidosis but they also have a cathartic effect. In fact, magnesium oxide and magnesium hydroxide are ideal chemicals for the treatment of grain overload in cattle. The combination of antacid activity which neutralizes excess acid in the rumen and cathartic activity which stimulates passage of toxic material out of the digestive tract is very beneficial. Tables I and 2 list some commercially available antacids for use in ruminants for the treatment of grain overload or acid indigestion. Generally, the powders contain magnesium oxide as the active ingredient or a mixture of magnesium oxide and magnesium hydroxide. Boluses, on the other hand usually contain magnesium hydroxide. Although these compounds are very efficacious as antacids in the treatment of grain overload, a problem associated with their use has recently been noted at O.V.C. A number of adult cattle have, at presentation, exhibited a profound metabolic alkalosis with no detectable abomasal abnormality. A frequent history in these cases has been the prior administration via stomach tube or by drench bottle of magnesium oxide or magnesium hydroxide as a cathartic or rumen stimulant for the treatment of acute or chronic anorexia. Invariably these compounds have been administered as one of the aforementioned commercially available antacid products. Accordingly, several questions arose as a result of these baffling cases.